Photoactive compounds for vapor deposited organic photovoltaic devices

ABSTRACT

Photoactive compounds are disclosed. The disclosed compounds can exhibit molecular structural elements tending to increase the evaporability of the compounds, such as by including geometric core disruption by use of conformationally restricted side groups instead of freely rotatable side groups or use of indandione moieties instead of dicyanomethyleneindanone moieties. The disclosed photoactive compounds include those with an imine-bridging linking moiety, which can shift the optical properties to a more red-shifted absorbance as compared to compounds with an alkene-bridging linking moiety. The disclosed photoactive compounds can be used in organic photovoltaic devices, such as visibly transparent or opaque photovoltaic devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 63/109,722, filed on Nov. 4, 2020, U.S. ProvisionalApplication No. 63/140,744, filed on Jan. 22, 2021, and U.S. ProvisionalApplication No. 63/141,387, filed on Jan. 25, 2021, U.S. ProvisionalApplication No. 63/140,758, filed on Jan. 22, 2021, U.S. ProvisionalApplication No. 63/141,390, filed on Jan. 25, 2021, and U.S. ProvisionalApplication No. 63/275,311, filed on Nov. 3, 2021, which are herebyincorporated by reference in their entireties.

FIELD

This application relates generally to the field of optically activematerials and devices, and, more particularly, to photoactive materialsfor use in organic photovoltaic devices, photovoltaic devices, andmethods for making photovoltaic devices.

BACKGROUND

The surface area necessary to take advantage of solar energy remains anobstacle to offsetting a significant portion of non-renewable energyconsumption. For this reason, low-cost, transparent, organicphotovoltaic (OPV) devices that can be integrated onto window panes inhomes, skyscrapers, and automobiles are desirable. For example, windowglass utilized in automobiles and architecture are typically 70-80% and55-90% transmissive, respectively, to the visible spectrum, e.g., lightwith wavelengths from about 450 to 650 nanometers (nm). The limitedmechanical flexibility, high module cost and, more importantly, theband-like absorption of inorganic semiconductors limit their potentialutility to transparent solar cells.

In contrast, the optical characteristics of organic and molecularsemiconductors results in absorption spectra that are highly structuredwith absorption minima and maxima that are uniquely distinct from theband absorption of their inorganic counterparts. However, a variety oforganic and molecular semiconductors exist, but many of exhibit strongabsorption in the visible spectrum and thus are not optimal for use inwindow glass-based photovoltaics.

Fullerene electron acceptors, such as C₆₀ and C₇₀, have been usedhistorically in different organic photovoltaic solar cell architectures.However, due to the absorbance overlap in the visible region and issueswith cost and purification, there has been interest in the developmentof NFAs (Non-Fullerene Acceptors). One class of NFAs is based on themolecule ITIC(3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene),which contains an indacenedithione[3,2-b]thiophene core (IT), with four4-hexylphenyl groups, and capped with2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (INCN) groups. Thisand related ITIC-style acceptors are generally regarded as highperforming NFA materials, but they cannot be deposited through physicalvapor deposition. All known examples of devices containing ITIC-styleacceptors are produced through solution-based processing. Solution basedITIC-style material containing devices have set world recordperformances for opaque organic photovoltaics, but challenges exist formanufacturing at scale using solution-based processing.

SUMMARY

Described herein are materials, methods, and systems related to organicphotovoltaic devices and, in some cases, especially useful for visiblytransparent organic photovoltaic devices as well as partiallytransparent organic photovoltaic devices and opaque organic photovoltaicdevices. More particularly, the present description provides photoactivecompounds, such as useful as acceptor molecules or donor molecules, andmethods and systems incorporating the disclosed compounds as aphotoactive material of a photovoltaic device.

The disclosed photoactive compounds include those having a formula ofA-D-A, A-pi-D-A, or A-pi-D-pi-A, where A is an electron acceptor moiety,pi is a π-bridging moiety, and D is an electron donor moiety. In somecases, photoactive compounds may have a formula of A-D or A-pi-D.Variations on A, D, and pi moieties are described herein, but thesemoieties may be selected so as to provide an absorption andelectrochemical character suitable for use as an electron donor moleculeor an electron acceptor in an organic photovoltaic device. The disclosedphotoactive compounds may be suitable for purification using sublimationand for deposition on a surface using a vacuum deposition process, likevacuum thermal evaporation. For example, their sublimation temperaturemay be lower than the temperature at which they thermally decompose. Theidentity, molecular weight, and structures of the A, D, and pi moietiesmay impact the volatility of the photoactive compounds in various ways,as described in further detail below.

In some examples, the D moiety in a photoactive compound may comprise afused aromatic ring structure, such as containing one or more 5-memberedrings and/or one or more 6-membered rings, with the rings optionallybeing carbocyclic rings or heterocyclic rings, such as containing one ormore heteroatoms, like O, S, Se, N, Si, or Ge. The D moiety may alsoinclude one or more side groups, which may be referred to as Z groups orZ moieties. These Z groups may be bonded to carbon atoms in the fusedring structure, and optionally with multiple Z groups bonded to the samecarbon atom, which may be a quaternary center, such as a quaternary C,Si, or Ge. Example Z groups may be alkyl groups, alkenyl group, orphenyl group, which may be substituted or unsubstituted. In some cases,two Z groups can form a ring.

In some examples, the Z groups may be referred to as planaritydisrupting moieties or disrupting moieties, in that these groups mayextend out from the plane of a fused aromatic ring structure and includea structure that conformationally or sterically locks the atoms of the Zgroup in a fixed position out-of-plane with the fused aromatic ringstructure. This out-of-plane conformational can disrupt the crystalpacking structure, for example, altering properties of the photoactivecompound relating to melting, sublimation, or vapor pressure. In somecases, the disruption can make the photoactive compound more suitablefor deposition using physical vapor deposition processes or forpurifying by sublimation. In other cases, the Z groups may not result insignificant disruption to the planar configuration of the fused aromaticring structure.

In some examples, the A moiety in a photoactive compound may comprise anindanone, an indandione, an indanthione, an indandithione, adicyanomethyleneindanone, or a bis(dicyanomethylidene)indan. In somecases, indandiones may be referred to as indanediones. In some cases,indanthiones may be referred to as thioxoindanone. In some cases,indandithiones may be referred to as indanedithiones. In some cases,dicyanomethyleneindanones may be referred to as malononitrile indanones.In some cases bis(dicyanomethylidene)indans may be referred to asdimalononitrile indanes. Other A moieties may also or alternatively beincluded in a photoactive compound, such as A moieties comprisingfive-membered and/or six-membered rings, which may include one or moreheteroatoms, such as thiophene or other heterocyclic rings. In otherexamples, an A moiety may comprise a vinylic cyano-ester linkedcompound.

Optionally, the A moiety may be bonded to a D moiety or a pi moiety by acarbon-carbon bond (carbon linkage) or include a nitrogen atom and bebonded to a D moiety or a pi moiety by a nitrogen carbon bond (iminelinkage). Use of an imine-linked A moiety may alter the spectroscopicproperties of the photoactive compound, such as inducing a red-shift ascompared to the same compound but using a carbon linkage instead of animine linkage.

In some examples, the pi moiety may comprise an aromatic orheteroaromatic structure including one or more 5-membered rings and/orone or more 6-membered rings, with a bi-radical structure, providing alink between an A moiety and the D moiety. Examples of pi moieties mayinclude, but are not limited to, thiophenes and fused thiophenes.

As noted above, the photoactive compounds may be suitable for depositionusing vacuum deposition techniques like vacuum thermal evaporation. Insome cases, the molecular weight of the photoactive compounds may impactthe volatility of the compounds, as compounds that have a very highmolecular weight may end up thermally decomposing before they evaporateor sublime. In some examples, an upper limit on the molecular weight ofa photoactive compound may be about 1200 atomic mass units.

Photovoltaic devices incorporating the photoactive compounds, methods ofmaking the photoactive compounds, and methods of making photovoltaicdevices incorporating the photoactive compounds are also describedherein.

These and other examples, embodiments, and aspects of the inventionalong with many advantages and features are described in more detail inconjunction with the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a schematic representation of a photoactive compound inaccordance with some examples.

FIG. 2 provides a schematic representation of another photoactivecompound in accordance with some examples.

FIG. 3A is a simplified schematic diagram illustrating a visiblytransparent photovoltaic device according to some examples.

FIG. 3B provides an overview of various configurations of photoactivelayer(s) in visibly transparent photovoltaic devices according to someexamples.

FIG. 4 is simplified plot illustrating the solar spectrum, human eyesensitivity, and exemplary transparent photovoltaic device absorption asa function of wavelength.

FIG. 5 is a simplified energy level diagram for a visibly transparentphotovoltaic device according to some examples.

FIG. 6A, FIG. 6B, FIG. 6C, and FIG. 6D provide plots showing exampleabsorption profiles for different electron acceptor and electron donorconfigurations, which can comprise the photoactive layers.

FIG. 7 provides an overview of a method of making visibly transparentphotovoltaic devices according to some examples.

FIG. 8 provides a synthetic scheme for preparation of an examplecompound useful in preparing various core-disrupted photoactivecompounds.

FIG. 9 provides synthetic schemes for preparation of various examplecore-disrupted photoactive compounds.

FIG. 10 provides synthetic schemes for preparation of various examplecore-disrupted photoactive compounds.

FIG. 11 provides a synthetic scheme for preparation of an examplecore-disrupted photoactive compound.

FIG. 12 provides a synthetic scheme for preparation of an examplecore-disrupted photoactive compound.

FIG. 13 provides a synthetic scheme for preparation of an examplecore-disrupted photoactive compound.

FIG. 14 provides a synthetic scheme for preparation of an examplecompound useful in preparing various photoactive compounds.

FIG. 15 provides synthetic schemes for preparation of various examplephotoactive compounds.

FIG. 16 provides a synthetic scheme for preparation of an exampleindandione-containing photoactive compound.

FIG. 17 provides a synthetic scheme for preparation of an examplecore-disrupted, indandione-containing photoactive compound.

FIG. 18 provides a synthetic scheme for preparation of an examplecore-disrupted, indandione-containing photoactive compound.

FIG. 19 provides a synthetic scheme for preparation of an examplecore-disrupted, indandione-containing photoactive compound.

FIG. 20 provides synthetic schemes for preparation of examplecore-disrupted photoactive compounds.

FIG. 21 provides a synthetic scheme for preparation of an examplecompound useful in preparing various photoactive compounds.

FIG. 22 provides synthetic schemes for preparation of various examplephotoactive compounds.

FIG. 23 provides a synthetic scheme for preparation of an examplephotoactive compound.

FIG. 24 provides a synthetic scheme for preparation of an examplecompound useful in preparing various core-disrupted photoactivecompounds including a quaternary silicon center.

FIG. 25 provides synthetic schemes for preparation of various examplecore-disrupted photoactive compounds.

FIG. 26 provides a synthetic scheme for preparation of an examplephotoactive compound.

FIG. 27 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 28 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 29 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 30 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 31 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 32 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 33 provides a synthetic scheme for preparation of an exampleindandione containing photoactive compound.

FIG. 34 provides synthetic schemes for preparation of example indandionecontaining photoactive compounds.

FIG. 35 provides a synthetic scheme showing preparation of an examplephotoactive compound in accordance with some examples.

FIG. 36 provides a plot showing normalized absorbance by examplephotoactive compounds in accordance with some examples.

FIG. 37 provides a plot showing sublimation yield of example photoactivecompounds in accordance with some examples.

FIG. 38 provides absorption coefficients for example photoactivecompounds for which transparent photovoltaic devices were constructed.

FIG. 39A, FIG. 39B, FIG. 39C, and FIG. 39D provides schematicillustrations of example photovoltaic device structures.

FIG. 40A provides a plot showing current density-voltage curves for thephotovoltaic devices illustrated in FIGS. 39A-39D.

FIG. 40B provides a plot showing external quantum efficiency curves forthe photovoltaic devices illustrated in FIGS. 39A-39D.

FIG. 40C provides a plot showing transmission spectra for thephotovoltaic devices illustrated in FIGS. 39A-39D.

DETAILED DESCRIPTION

The present disclosure relates to photoactive compounds, which may beuseful as electron acceptor compounds or electron donor compounds,photovoltaic devices incorporating the disclosed photoactive compoundsas photoactive materials, and methods of making and using photovoltaicdevices. The disclosed photoactive compounds possess properties, such asrelatively low molecular weights, relatively high vapor pressures, orthe like, that allow for the compounds to be purified and/or depositedusing vapor phase techniques such as sublimation, vacuum thermalevaporation, and physical vapor deposition. In addition, the photoactivecompounds exhibit strong absorption, allowing for use in organicphotovoltaic devices. In some cases, the photoactive compounds exhibitabsorption of light more strongly in the near-infrared and/orultraviolet regions and less strongly in the visible region, permittingtheir use in visibly transparent photovoltaic devices. In other cases,the photoactive compounds are useful in transparent and opaquephotovoltaic devices.

The disclosed photoactive compounds include those with specific featuresthat may provide advantages for use as electron acceptors but may alsobe useful as electron donors in some cases depending on the pairing ofthe photoactive compounds with other compounds in an organicphotovoltaic device. The disclosed compounds may exhibit a molecularstructure where different moieties or sub-structures are bonded to oneanother, such as electron donor moieties (D), electron acceptor moieties(A), and π-bridging moieties (pi). These components may be arranged inany suitable arrangement to form a photoactive compound. Moreover, eachof the different components may include certain structural/compositionalfeatures that can impact various properties of the photoactive compound,such as the band gap, the sublimation enthalpy, the sublimationtemperature, or the crystal packing density, for example

For example, some of the disclosed compounds may exhibit a structure orhave formula of A-D-A or A-D. FIG. 1 provides a schematic representationof a photoactive compound 100 having an A-D-A structure. FIG. 1 shows afirst electron acceptor moiety 105, a second electron acceptor moiety110, and an electron donor moiety 115 between first electron acceptormoiety 105 and second electron acceptor moiety 110. In cases where thephotoactive compound 100 has an A-D structure, second electron acceptormoiety 110 may not be present and electron donor moiety 115 may includea small group, such as a hydrogen atom, an alkyl group, an alkylenegroup, or the like, at the position where second electron acceptormoiety 110 would otherwise be present. Optionally, the first electronacceptor moiety 105 and the second electron acceptor moiety 110 can bethe same. Optionally, the first electron acceptor moiety 105 and thesecond electron acceptor moiety 110 can be different.

In some cases, π-bridging moieties may be positioned between A and Dmoieties, such that the disclosed compounds may exhibit a structure orhave formula of A-pi-D-A, A-pi-D-pi-A, or A-pi-D. FIG. 2 provides aschematic representation of a photoactive compound 200 having anA-pi-D-pi-A structure. FIG. 2 shows a first electron acceptor moiety205, a second electron acceptor moiety 210, an electron donor moiety215, a first π-bridging moiety 220, and a second π-bridging moiety 225.As shown, first π-bridging moiety 220 is positioned between firstelectron acceptor moiety 205 and electron donor moiety 215, and secondπ-bridging moiety 225 is positioned between electron donor moiety 215and second electron acceptor moiety 210. In cases where the photoactivecompound 200 has an A-pi-D-A structure, second π-bridging moiety 225 maynot be present. In cases where the photoactive compound 200 has anA-pi-D structure, second electron acceptor moiety 210 may not be presentand electron donor moiety 215 may include a small group, such as ahydrogen atom, an alkyl group, an alkylene group, or the like, at theposition where second electron acceptor moiety 210 would otherwise bepresent. In some examples, second π-bridging moiety 225 may also not bepresent. Optionally, the first electron acceptor moiety 205 and thesecond electron acceptor moiety 210 can be the same. Optionally, thefirst electron acceptor moiety 205 and the second electron acceptormoiety 210 can be different. Optionally, the first π-bridging moiety 220and the second π-bridging moiety 225 can be the same. Optionally, thefirst π-bridging moiety 220 and the second π-bridging moiety 225 can bedifferent.

As depicted, electron donor moiety 115 and 215 can have varioussubcomponents, which may contribute certain features. For example,electron donor moiety 115 or 215 can comprise a central core 130 or 230and a side group 135 or 235. In some electron donors, central core 130or 230 may have or exhibit an electron rich planar molecular structure,such as where one or more carbon atoms, and optionally one or moreheteroatoms, are arranged in a plane. In some cases, central core 130 or230 may comprise an aromatic or heteroaromatic structure, optionallyincluding one or more 5-membered rings, one or more 6-membered rings, orone or more 5-membered rings and one or more 6-membered rings, such asin a fused ring configuration.

Side group 135 or 235 may comprise any suitable organic group,optionally including one or more heteroatoms. In some cases, side group135 or 235 may adopt any molecular arrangement, such as by includingbonds allowing for free rotation. In other cases, however, the atomsmaking up side group 135 or 235 may have a bonding configuration lockingthe atoms in a particular geometry. For example, side group 135 or 235may be or comprise one or more planarity disrupting moieties that areconformationally locked in a configuration out of plane to central core130 or 230. Without wishing to be bound by any theory, the inclusion ofa side group that is a planarity disrupting moiety can impact theability of molecules of photoactive compound 100 or 200 to form tightlypacked crystals in the bulk, as the planarity disrupting moieties canprovide a molecular structure that forces an overall non-planarmolecular geometry. Such a configuration can result in a decrease incrystal packing density, for example. Other properties, such as enthalpyof melting, evaporation, or sublimation, melting temperature, boilingtemperature, or sublimation temperature may also be impacted. Thus, byincluding planarity disrupting moieties in the chemical structure,photoactive compound 100 or 200 can be more suitable for purificationusing sublimation processes or more suitable for deposition by gas phasedeposition processes, like vacuum thermal evaporation. In some cases,use of a planarity disrupting moiety can increase the evaporability ofthe photoactive compound, such as to a level greater than a comparablephotoactive compounds having the same electron acceptor moieties,pi-bridging moieties (if present), and central core, but including sidegroup(s) that are not a planarity disrupting moiety but that have thesame or about the same molecular weight.

Electron donor groups 105, 110, 205 or 220 can have varioussubcomponents, which may contribute certain features. For example, insome cases, one or more of electron acceptor groups 105, 110, 205, or220 can comprise a specific composition, such as an indandione, anaryl-substituted indandione, an indanthione, an aryl-substitutedindanthione, an indandithione, or an aryl-substituted indandithione.These compositions may contrast with other electron acceptor groups thatmay be used for some photoactive molecules, such asdicyanomethyleneindanone or bis(dicyanomethylidene)indan groups, whichcontain dicyanovinyl groups or ═C(CN)₂ groups. However, such aconfiguration is not limiting and some electron acceptor groups maycomprise indandione, aryl-substituted indandione, indanthione,aryl-substituted indanthione, indandithione, aryl-substitutedindandithione, dicyanomethyleneindanone, or bis(dicyanomethylidene)indangroups or other electron acceptor groups. In some specific cases of aphotoactive compound having two A components, one A can comprise adicyanovinyl containing group and the other A can contain an indandione,an aryl-substituted indandione, a indanthione, an aryl-substitutedindanthione, an indandithione, or an aryl-substituted indandithione.Photoactive compounds incorporating one or more indandione,aryl-substituted indandione, indanthione, aryl-substituted indanthione,indandithione, aryl-substituted indandithione groups as electronacceptor groups may be more suitable for purification by sublimation ormore suitable for vapor deposition, such as using a thermal evaporationtechnique, than comparable photoactive compounds containing onlydicyanomethyleneindanone, or bis(dicyanomethylidene)indan groups. Forexample, in some cases, use of an indandione, indanthione, orindandithione groups as electron acceptor groups can increase thevolatility of the photoactive compound, such as to a level greater thana comparable photoactive compound having the same pi-bridging moieties(if present) and central core, but including dicyanomethyleneindanone orbis(dicyanomethylidene)indan groups instead of indandione, indanthione,or indandithione groups. In some cases, even substitution of onedicyanomethyleneindanone or bis(dicyanomethylidene)indan group for anindandione, indanthione, or indandithone group can result in asignificant increase in the volatility.

As another example, electron acceptor groups 105, 110, 205, or 220 cancomprise a specific linking structure at the point where electronacceptor groups 105, 110, 205, or 220 is bonded to electron donor groups115 or 215 or π-bridging groups 220 or 225. For example, in some caseselectron acceptor groups 105, 110, 205, or 220 can comprise an iminebond, ═N—, as a linking group, where the single bond corresponds to abond to an adjacent A or pi group and the double bond corresponds to abond to another portion of the electron acceptor group. In other cases,electron acceptor groups 105, 110, 205, or 220 can comprise an alkenebond, ═CH—, as a linking group, where the single bond corresponds to abond to an adjacent A or pi group and the double bond corresponds to abond to another portion of the electron acceptor group. Inclusion of animine bond can be useful for modifying the band gap or absorptionmaximum of the photoactive compound 100 or 200. For example, in somecases inclusion of an imine bond can result in a redshift in the bandgap or a redshift in the absorption maximum of a photoactive compound,as compared to a photoactive compound with an otherwise identicalstructure but containing an alkene bond instead of the imine bond.Preparation of photoactive compounds containing an imine bond mayrequire a different synthetic route than used for preparing photoactivecompounds lacking an imine bond.

In some examples, for purification and use of the disclosed photoactivecompounds, a very high molecular weight may be undesirable, such asabout 1200 amu or higher, about 1150 amu or higher, about 1100 amu orhigher, about 1050 amu or higher, about 1000 amu or higher, about 950amu or higher, about 900 amu or higher, or between 900 amu and 2000 amuor a subrange thereof. Some compounds with very high molecular weightsmay have limited volatilities and useful methods of purifying and usingphotoactive compounds may employ an evaporation or sublimation-basedmethod. In addition, the photoactive compounds may be deposited as partof a photovoltaic device using a thermal evaporation technique andcompounds of very high molecular weight may be difficult to depositusing thermal evaporation. In various examples, the photoactivecompounds described herein have a molecular weight of 200 amu to 1200amu, less than or about 1200 amu, less than or about 1150 amu, less thanor about 1100 amu, less than or about 1050 amu, less than or about 1000amu, less than or about 950 amu, less than or about 900 amu, less thanor about 850 amu, less than or about 800 amu, less than or about 750amu, less than or about 700 amu, less than or about 650 amu, less thanor about 600 amu, less than or about 550 amu, less than or about 500amu, less than or about 450 amu, less than or about 400 amu, less thanor about 350 amu, less than or about 300 amu, less than or about 250amu, or less than or about 200 amu.

To achieve desired optical properties, photoactive compounds may exhibita molecular electronic structure where photons of light are absorbed,which results in promotion of an electron to a higher molecular orbital,with an energy difference matching that of the absorbed photon, whichmay result in generation of an electron-hole pair or exciton, which cansubsequently separate into distinct electrons and holes, such as at aninterface with another material. Compounds exhibiting extendedaromaticity or extended conjugation may be beneficial, as compounds withextended aromaticity or extended conjugation may exhibit electronicabsorption with energies matching that of near-infrared, visible, and/orultraviolet photons. In addition to conjugation and aromaticity,absorption features may be modulated by inclusion of heteroatoms in theorganic structure of the visibly transparent photoactive compounds, suchas oxygen, nitrogen, or sulfur atoms.

In general the terms and phrases used herein have their art-recognizedmeaning, which can be found by reference to standard texts, journalreferences and contexts known to those skilled in the art. The followingdefinitions are provided to clarify their specific use in the context ofthe invention.

As used herein, “maximum absorption strength” refers to the largestabsorption value in a particular spectral region, such as theultraviolet band (e.g., from 200 nm to 450 nm or from 280 nm to 450 nm),the visible band (e.g., from 450 nm to 650 nm), or the near-infraredband (e.g., from 650 nm to 1400 nm), of a particular molecule, forexample. In some examples, a maximum absorption strength may correspondto an absorption strength of an absorption feature that is a local orabsolute maximum, such as an absorption band or peak, and may bereferred to as a peak absorption. In some examples, a maximum absorptionstrength in a particular band may not correspond to a local or absolutemaximum but may instead correspond to the largest absorption value inthe particular band. Such a configuration may occur, for example, whenan absorption feature spans multiple bands (e.g., visible andnear-infrared), and the absorption values from the absorption featurethat occur within one band are smaller than those occurring within theadjacent band, such as when the peak of the absorption feature islocated within the near-infrared band but a tail of the absorptionfeature extends to the visible band. In some examples, a photoactivecompound described herein may having an absorption peak at a wavelengthgreater than about 650 nanometers (e.g., in the near-infrared), and thephotoactive compound's absorption peak may be greater in magnitude thanthe photoactive compound's absorption at any wavelength between about450 and 650 nanometers.

In various examples, disclosed compositions or compounds are isolated orpurified. Optionally, an isolated or purified compound is at leastpartially isolated or purified as would be understood in the art. Insome examples, a disclosed composition or compound has a chemical purityof 80%, optionally for some applications 90%, optionally for someapplications 95%, optionally for some applications 99%, optionally forsome applications 99.9%, optionally for some applications 99.99%, andoptionally for some applications 99.999% pure. Purification of thedisclosed compositions or compounds may be performed using any desirabletechnique. Purification by chromatography, vacuum sublimation, and/orcrystallization may be particularly useful techniques.

Compounds disclosed herein optionally contain one or more ionizablegroups. Ionizable groups include groups from which a proton can beremoved (e.g., —COOH) or added (e.g., amines) and groups which can bequaternized (e.g., amines). All possible ionic forms of such moleculesand salts thereof are intended to be included individually in thedisclosure herein. With regard to salts of the compounds describedherein, it will be appreciated that a wide variety of availablecounter-ions may be selected that are appropriate for preparation ofsalts for a given application. In specific applications, the selectionof a given anion or cation for preparation of a salt can result inincreased or decreased solubility of that salt.

The disclosed compounds optionally contain one or more chiral centers.Accordingly, this disclosure includes racemic mixtures, diastereomers,enantiomers, tautomers and mixtures enriched in one or morestereoisomer. Disclosed compounds including chiral centers encompass theracemic forms of the compound as well as the individual enantiomers andnon-racemic mixtures thereof.

As used herein, the terms “group” and “moiety” may refer to a functionalgroup of a chemical compound. Groups of the disclosed compounds refer toan atom or a collection of atoms that are a part of the compound. Groupsof the disclosed compounds may be attached to other atoms of thecompound via one or more covalent bonds. Groups may also becharacterized with respect to their valence state. The presentdisclosure includes groups characterized as monovalent, divalent,trivalent, etc. valence states. Optionally, the term “substituent” maybe used interchangeably with the terms “group” and “moiety.” Groups mayalso be characterized with respect to their ability to donate or receivean electron, and such characterization may, in some examples, refer to arelative character of the group to donate or receive an electron ascompared to other groups.

As is customary and well known in the art, hydrogen atoms in chemicalformulas disclosed herein are not always explicitly shown, for example,hydrogen atoms bonded to the carbon atoms of aliphatic, aromatic,alicyclic, carbocyclic, and/or heterocyclic rings are not alwaysexplicitly shown in the formulas recited. The structures providedherein, for example in the context of the description of any specificformulas and structures recited, are intended to convey the chemicalcomposition of disclosed compounds of methods and compositions. It willbe appreciated that the structures provided do not indicate the specificpositions of atoms and bond angles between atoms of these compounds. Asused herein, a wavy line at an end of a bond in a structure or formularepresents the position where the indicated moiety connects or can beconnected to another moiety. For example, a wavy line in an A moiety canbe paired to a wavy line in a D or pi moiety to form an A-D moiety or anA-pi moiety. In some cases, a wavy line in a D moiety may correspond toa hydrogen atom. For example, for A-D or A-pi-D compounds, some Dmoieties described herein are shown with two wavy lines, one of whichcan connect to a hydrogen atom.

As used herein, the terms “alkylene” and “alkylene group” are usedsynonymously and refer to a divalent group derived from an alkyl groupas defined herein. The present disclosure includes compounds having oneor more alkylene groups. Alkylene groups in some compounds function asattaching and/or spacer groups. Disclosed compounds optionally includesubstituted and/or unsubstituted C₁-C₂₀ alkylene, C₁-C₁₀ alkylene, orC₁-C₅ alkylene groups.

As used herein, the terms “cycloalkylene” and “cycloalkylene group” areused synonymously and refer to a divalent group derived from acycloalkyl group as defined herein. The present disclosure includescompounds having one or more cycloalkylene groups. Cycloalkylene groupsin some compounds function as attaching and/or spacer groups. Disclosedcompounds optionally include substituted and/or unsubstituted C₃-C₂₀cycloalkylene, C₃-C₁₀ cycloalkylene, or C₃-C₅ cycloalkylene groups.

As used herein, the terms “arylene” and “arylene group” are usedsynonymously and refer to a divalent group derived from an aryl group asdefined herein. The present disclosure includes compounds having one ormore arylene groups. In some examples, an arylene is a divalent groupderived from an aryl group by removal of hydrogen atoms from twointra-ring carbon atoms of an aromatic ring of the aryl group. Arylenegroups in some compounds function as attaching and/or spacer groups.Arylene groups in some compounds function as chromophore, fluorophore,aromatic antenna, dye, and/or imaging groups. Disclosed compoundsoptionally include substituted and/or unsubstituted C₅-C₃₀ arylene,C₅-C₂₀ arylene, or C₅-C₁₀ arylene groups.

As used herein, the terms “heteroarylene” and “heteroarylene group” areused synonymously and refer to a divalent group derived from aheteroaryl group as defined herein. The present disclosure includescompounds having one or more heteroarylene groups. In some examples, aheteroarylene is a divalent group derived from a heteroaryl group byremoval of hydrogen atoms from two intra-ring carbon atoms or intra-ringnitrogen atoms of a heteroaromatic or aromatic ring of the heteroarylgroup. Heteroarylene groups in some compounds function as attachingand/or spacer groups. Heteroarylene groups in some compounds function aschromophore, aromatic antenna, fluorophore, dye, and/or imaging groups.Disclosed compounds optionally include substituted and/or unsubstitutedC₅-C₃₀ heteroarylene, C₅-C₂₀ heteroarylene, or C₅-C₁₀ heteroarylene.

As used herein, the terms “alkenylene” and “alkenylene group” are usedsynonymously and refer to a divalent group derived from an alkenyl groupas defined herein. The present disclosure includes compounds having oneor more alkenylene groups. Alkenylene groups in some compounds functionas attaching and/or spacer groups. Disclosed compounds optionallyinclude substituted and/or unsubstituted C₂-C₂₀ alkenylene, C₂-C₁₀alkenylene, or C₂-C₅ alkenylene groups.

As used herein, the terms “cycloalkenylene” and “cycloalkenylene group”are used synonymously and refer to a divalent group derived from acycloalkenyl group as defined herein. The present disclosure includescompounds having one or more cycloalkenylene groups. Cycloalkenylenegroups in some compounds function as attaching and/or spacer groups.Disclosed compounds optionally include substituted and/or unsubstitutedC₃-C₂₀ cycloalkenylene, C₃-C₁₀ cycloalkenylene, or C₃-C₅ cycloalkenylenegroups.

As used herein, the terms “alkynylene” and “alkynylene group” are usedsynonymously and refer to a divalent group derived from an alkynyl groupas defined herein. The present disclosure includes compounds having oneor more alkynylene groups. Alkynylene groups in some compounds functionas attaching and/or spacer groups. Disclosed compounds optionallyinclude substituted and/or unsubstituted C₂-C₂₀ alkynylene, C₂-C₁₀alkynylene, or C₂-C₅ alkynylene groups.

As used herein, the term “halo” refers to a halogen group, such as afluoro (—F), chloro (—Cl), bromo (—Br), or iodo (—I).

The term “heterocyclic” refers to ring structures containing at leastone other kind of atom, in addition to carbon, in the ring. Examples ofsuch atoms include oxygen, sulfur, selenium, tellurium, nitrogen,phosphorus, silicon, germanium, boron, aluminum, and, in some cases, atransition metal. Examples of heterocyclic rings include, but are notlimited to, pyrrolidinyl, piperidyl, imidazolidinyl, tetrahydrofuranyl,tetrahydrothienyl, furanyl, thienyl, pyridyl, quinolyl, isoquinolyl,pyridazinyl, pyrazinyl, indolyl, imidazolyl, oxazolyl, thiazolyl,pyrazolyl, pyridinyl, benzoxadiazolyl, benzothiadiazolyl, triazolyl, andtetrazolyl groups. Atoms of heterocyclic rings can be bonded to a widerange of other atoms and functional groups, for example, provided assubstituents. Heterocyclic rings include aromatic heterocycles andnon-aromatic heterocycles.

The term “carbocyclic” refers to ring structures containing only carbonatoms in the ring. Carbon atoms of carbocyclic rings can be bonded to awide range of other atoms and functional groups, for example, providedas substituents. Carbocyclic rings include aromatic carbocyclic ringsand non-aromatic carbocyclic rings.

The term “alicyclic” refers to a ring that is not an aromatic ring.Alicyclic rings include both carbocyclic and heterocyclic rings.

The term “aliphatic” refers to non-aromatic hydrocarbon compounds andgroups. Aliphatic groups generally include carbon atoms covalentlybonded to one or more other atoms, such as carbon and hydrogen atoms.Aliphatic groups may, however, include a non-carbon atom, such as anoxygen atom, a nitrogen atom, a sulfur atom, etc., in place of a carbonatom. Non-substituted aliphatic groups include only hydrogensubstituents. Substituted aliphatic groups include non-hydrogensubstituents, such as halo groups and other substituents describedherein. Aliphatic groups can be straight chain, branched, or cyclic.Aliphatic groups can be saturated, meaning only single bonds joinadjacent carbon (or other) atoms. Aliphatic groups can be unsaturated,meaning one or more double bonds or triple bonds join adjacent carbon(or other) atoms.

Alkyl groups include straight-chain, branched, and cyclic alkyl groups.Alkyl groups include those having from 1 to 30 carbon atoms. Alkylgroups include small alkyl groups having 1 to 3 carbon atoms. Alkylgroups include medium length alkyl groups having from 4-10 carbon atoms.Alkyl groups include long alkyl groups having more than 10 carbon atoms,particularly those having 10-30 carbon atoms. The term cycloalkylspecifically refers to an alky group having a ring structure such asring structure comprising 3-30 carbon atoms, optionally 3-20 carbonatoms and optionally 3-10 carbon atoms, including an alkyl group havingone or more rings. Cycloalkyl groups include those having a 3-, 4-, 5-,6-, 7-, 8-, 9-, or 10-member carbon ring(s) and particularly thosehaving a 3-, 4-, 5-, 6-, or 7-member ring(s). The carbon rings incycloalkyl groups can also carry alkyl groups. Cycloalkyl groups caninclude bicyclic and tricycloalkyl groups. Alkyl groups are optionallysubstituted. Substituted alkyl groups include, among others, those whichare substituted with aryl groups, which in turn can be optionallysubstituted. Specific alkyl groups include methyl, ethyl, n-propyl,iso-propyl, cyclopropyl, n-butyl, branched butyl, cyclobutyl, n-pentyl,branched-pentyl, cyclopentyl, n-hexyl, branched hexyl, and cyclohexylgroups, all of which are optionally substituted. Substituted alkylgroups include fully-halogenated or semi-halogenated alkyl groups, suchas alkyl groups having one or more hydrogens replaced with one or morefluorine atoms, chlorine atoms, bromine atoms and/or iodine atoms.Substituted alkyl groups include fully-fluorinated or semi-fluorinatedalkyl groups, such as alkyl groups having one or more hydrogens replacedwith one or more fluorine atoms. Substituted alkyl groups include alkylgroups substituted with one or more methyl, ethyl, halogen (e.g.,fluoro), or trihalomethyl (e.g., trifluoromethyl) groups.

An alkoxy group is an alkyl group that has been modified by linkage tooxygen and can be represented by the formula R—O and can also bereferred to as an alkyl ether group. Examples of alkoxy groups include,but are not limited to, methoxy, ethoxy, propoxy, butoxy, pentoxy,hexoxy, and heptoxy. Alkoxy groups include substituted alkoxy groupswherein the alkyl portion of the groups is substituted as providedherein in connection with the description of alkyl groups. As usedherein MeO— refers to CH₃O—.

Alkenyl groups include straight-chain, branched, and cyclic alkenylgroups. Alkenyl groups include those having 1, 2, or more double bondsand those in which two or more of the double bonds are conjugated doublebonds. Alkenyl groups include those having from 2 to 20 carbon atoms.Alkenyl groups include small alkenyl groups having 2 to 4 carbon atoms.Alkenyl groups include medium length alkenyl groups having from 5-10carbon atoms. Alkenyl groups include long alkenyl groups having morethan 10 carbon atoms, particularly those having 10-20 carbon atoms.Cycloalkenyl groups include those in which a double bond is in the ringor in an alkenyl group attached to a ring. The term cycloalkenylspecifically refers to an alkenyl group having a ring structure,including an alkenyl group having a 3-, 4-, 5-, 6-, 7-, 8-, 9-, or10-member carbon ring(s) and particularly those having a 3-, 4-, 5-, 6-,or 7-member ring(s). The carbon rings in cycloalkenyl groups can alsocarry alkyl groups. Cycloalkenyl groups can include bicyclic andtricyclic alkenyl groups. Alkenyl groups are optionally substituted.Substituted alkenyl groups include among others those which aresubstituted with alkyl or aryl groups, which groups in turn can beoptionally substituted. Specific alkenyl groups include ethenyl,prop-1-enyl, prop-2-enyl, cycloprop-1-enyl, but-1-enyl, but-2-enyl,cyclobut-1-enyl, cyclobut-2-enyl, pent-1-enyl, pent-2-enyl, branchedpentenyl, cyclopent-1-enyl, hex-1-enyl, branched hexenyl, cyclohexenyl,all of which are optionally substituted. Substituted alkenyl groupsinclude fully-halogenated or semi-halogenated alkenyl groups, such asalkenyl groups having one or more hydrogens replaced with one or morefluorine atoms, chlorine atoms, bromine atoms, and/or iodine atoms.Substituted alkenyl groups include fully-fluorinated or semi-fluorinatedalkenyl groups, such as alkenyl groups having one or more hydrogen atomsreplaced with one or more fluorine atoms. Substituted alkenyl groupsinclude alkenyl groups substituted with one or more methyl, ethyl,halogen (e.g., fluoro), or trihalomethyl (e.g., trifluoromethyl) groups.

Aryl groups include groups having one or more 5-, 6- or 7-memberaromatic and/or heterocyclic aromatic rings. The term heteroarylspecifically refers to aryl groups having at least one 5-, 6-, or7-member heterocyclic aromatic rings. Aryl groups can contain one ormore fused aromatic and heteroaromatic rings or a combination of one ormore aromatic or heteroaromatic rings and one or more non-aromatic ringsthat may be fused or linked via covalent bonds. Heterocyclic aromaticrings can include one or more N, O, or S atoms in the ring, amongothers. Heterocyclic aromatic rings can include those with one, two orthree N atoms, those with one or two O atoms, and those with one or twoS atoms, or combinations of one or two or three N, O, or S atoms, amongothers. Aryl groups are optionally substituted. Substituted aryl groupsinclude among others those which are substituted with alkyl or alkenylgroups, which groups in turn can be optionally substituted. Specificaryl groups include phenyl, biphenyl groups, pyrrolidinyl,imidazolidinyl, tetrahydrofuranyl, tetrahydrothienyl, furanyl, thienyl,pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrazinyl, indolyl,imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridinyl, benzoxadiazolyl,benzothiadiazolyl, and naphthyl groups, all of which are optionallysubstituted. Substituted aryl groups include fully halogenated orsemi-halogenated aryl groups, such as aryl groups having one or morehydrogens replaced with one or more fluorine atoms, chlorine atoms,bromine atoms and/or iodine atoms. Substituted aryl groups include fullyfluorinated or semi-fluorinated aryl groups, such as aryl groups havingone or more hydrogens replaced with one or more fluorine atoms. Arylgroups include, but are not limited to, aromatic group-containing orheterocyclic aromatic group-containing groups corresponding to any oneof the following: benzene, naphthalene, naphthoquinone, diphenylmethane,fluorene, anthracene, anthraquinone, phenanthrene, tetracene,tetracenedione, pyridine, quinoline, isoquinoline, indoles, isoindole,pyrrole, imidazole, oxazole, thiazole, pyrazole, pyrazine, pyrimidine,purine, benzimidazole, furans, benzofuran, dibenzofuran, carbazole,acridine, acridone, phenanthridine, thiophene, benzothiophene,dibenzothiophene, xanthene, xanthone, flavone, coumarin, azulene, oranthracycline. As used herein, a group corresponding to the groupslisted above expressly includes an aromatic or heterocyclic aromaticgroup, including monovalent, divalent and polyvalent groups, of thearomatic and heterocyclic aromatic groups listed herein are provided ina covalently bonded configuration in the disclosed compounds at anysuitable point of attachment. In examples, aryl groups contain between 5and 30 carbon atoms. In examples, aryl groups contain one aromatic orheteroaromatic six-membered ring and one or more additional five- orsix-membered aromatic or heteroaromatic ring. In examples, aryl groupscontain between five and eighteen carbon atoms in the rings. Aryl groupsoptionally have one or more aromatic rings or heterocyclic aromaticrings having one or more electron donating groups, electron withdrawinggroups and/or targeting ligands provided as substituents. Substitutedaryl groups include aryl groups substituted with one or more methyl,ethyl, halogen (e.g., fluoro), or trihalomethyl (e.g., trifluoromethyl)groups.

Arylalkyl and alkylaryl groups are alkyl groups substituted with one ormore aryl groups wherein the alkyl groups optionally carry additionalsubstituents and the aryl groups are optionally substituted. Specificalkylaryl groups are phenyl-substituted alkyl groups, e.g., phenylmethylgroups. Alkylaryl and arylalkyl groups are alternatively described asaryl groups substituted with one or more alkyl groups wherein the alkylgroups optionally carry additional substituents and the aryl groups areoptionally substituted. Specific alkylaryl groups are alkyl-substitutedphenyl groups such as methylphenyl. Substituted arylalkyl groups includefully-halogenated or semi-halogenated arylalkyl groups, such asarylalkyl groups having one or more alkyl and/or aryl groups having oneor more hydrogens replaced with one or more fluorine atoms, chlorineatoms, bromine atoms, and/or iodine atoms.

As to any of the groups described herein which contain one or moresubstituents, it is understood that such groups do not contain anysubstitution or substitution patterns which are sterically impracticaland/or synthetically non-feasible. In addition, the disclosed compoundsinclude all stereochemical isomers arising from the substitution ofthese compounds. Optional substitution of alkyl groups includessubstitution with one or more alkenyl groups, aryl groups, or both,wherein the alkenyl groups or aryl groups are optionally substituted.Optional substitution of alkenyl groups includes substitution with oneor more alkyl groups, aryl groups, or both, wherein the alkyl groups oraryl groups are optionally substituted. Optional substitution of arylgroups includes substitution of the aryl ring with one or more alkylgroups, alkenyl groups, or both, wherein the alkyl groups or alkenylgroups are optionally substituted.

Optional substituents for any alkyl, alkenyl, or aryl group includessubstitution with one or more of the following substituents, amongothers:

halogen, including fluorine, chlorine, bromine, or iodine;

pseudohalides, including —CN;

—COOR where R is a hydrogen or an alkyl group or an aryl group or, morespecifically, where R is a methyl, ethyl, propyl, butyl, or phenylgroup, all of which are optionally substituted;

—COR where R is a hydrogen or an alkyl group or an aryl group or, morespecifically, where R is a methyl, ethyl, propyl, butyl, or phenylgroup, all of which are optionally substituted;

—CON(R)₂ where each R, independently of each other R, is a hydrogen oran alkyl group or an aryl group or, more specifically, where R is amethyl, ethyl, propyl, butyl, or phenyl group, all of which areoptionally substituted; and where R and R can optionally form a ringwhich can contain one or more double bonds and can contain one or moreadditional carbon atoms;

—OCON(R)₂ where each R, independently of each other R, is a hydrogen oran alkyl group or an aryl group and, more specifically, where R is amethyl, ethyl, propyl, butyl, or phenyl group, all of which areoptionally substituted; and where R and R can optionally form a ringwhich can contain one or more double bonds and can contain one or moreadditional carbon atoms;

—N(R)₂ where each R, independently of each other R, is a hydrogen, or analkyl group, or an acyl group or an aryl group or, more specifically,where R is a methyl, ethyl, propyl, butyl, phenyl, or acetyl group, allof which are optionally substituted; and where R and R can optionallyform a ring which can contain one or more double bonds and can containone or more additional carbon atoms;

—SR, where R is hydrogen or an alkyl group or an aryl group or, morespecifically, where R is hydrogen, methyl, ethyl, propyl, butyl, or aphenyl group, all of which are optionally substituted;

—SO₂R, or —SOR where R is an alkyl group or an aryl group or, morespecifically, where R is a methyl, ethyl, propyl, butyl, or phenylgroup, all of which are optionally substituted;

—OCOOR where R is an alkyl group or an aryl group;

—SO₂N(R)₂ where each R, independently of each other R, is a hydrogen, analkyl group, or an aryl group, all of which are optionally substituted,and wherein R and R can optionally form a ring which can contain one ormore double bonds and can contain one or more additional carbon atoms;

—OR where R is H, an alkyl group, an aryl group, or an acyl group, allof which are optionally substituted. In a particular example R can be anacyl, yielding —OCOR″ where R″ is a hydrogen or an alkyl group or anaryl group and more specifically where R″ is methyl, ethyl, propyl,butyl, or phenyl groups, all of which are optionally substituted.

Specific substituted alkyl groups include haloalkyl groups, particularlytrihalomethyl groups and specifically trifluoromethyl groups. Specificsubstituted aryl groups include mono-, di-, tri, tetra- andpenta-halo-substituted phenyl groups; mono-, di-, tri-, tetra-, penta-,hexa-, and hepta-halo-substituted naphthalene groups; 3- or4-halo-substituted phenyl groups, 3- or 4-alkyl-substituted phenylgroups, 3- or 4-alkoxy-substituted phenyl groups, 3- or4-RCO-substituted phenyl, 5- or 6-halo-substituted naphthalene groups.More specifically, substituted aryl groups include acetylphenyl groups,particularly 4-acetylphenyl groups; fluorophenyl groups, particularly3-fluorophenyl and 4-fluorophenyl groups; chlorophenyl groups,particularly 3-chlorophenyl and 4-chlorophenyl groups; methylphenylgroups, particularly 4-methylphenyl groups; and methoxyphenyl groups,particularly 4-methoxyphenyl groups.

The term “electron acceptor” refers to a chemical composition that canaccept an electron from another structure or compound. The term electronacceptor may be used, in some cases, in a relative sense to identify acharacteristic of a compound or a subgroup thereof as having a strongeraffinity for receiving an additional electron as compared to anothercompound or a subgroup. In an organic photovoltaic, an electron acceptormay be a compound having an ability to receive electrons from anelectron donor. An electron acceptor may be a photoactive compound thatgenerates an electron-hole pair (exciton) upon photoabsorption of lightand which can transfer generated holes to an electron donor.

The term “electron donor” refers to a chemical composition that candonate an electron to another structure or compound. The term electrondonor may be used, in some cases, in a relative sense to identify acharacteristic of a compound or a subgroup thereof as having a weakeraffinity for receiving an additional electron as compared to anothercompound or a subgroup. In an organic photovoltaic, an electron donormay be a compound having an ability to transfer electrons to an electronacceptor. An electron donor may be a photoactive compound that generatesan electron-hole pair (exciton) upon photoabsorption of light and whichcan transfer generated electrons to an electron acceptor.

A “planarity disrupting moiety” or “disrupting moiety” refers to moietyor subgroup of a compound with an atomic arrangement (e.g., ofnon-hydrogen atoms, like carbon atoms and/or heteroatoms) that deviatesfrom the arrangement of atoms (e.g., a planar arrangement ofnon-hydrogen atoms, like carbon atoms and/or heteroatoms) of anotherpart of the compound. In one example, a compound can include a planarmoiety, where all or most of the non-hydrogen atoms (e.g., carbon and/orheteroatoms), and optionally hydrogen atoms, fall within a plane in thechemical structure of the atoms, and also include a planarity disruptingmoiety with atoms (e.g., non-hydrogen atoms like carbon and/orheteroatoms) that extend outside of or deviate significantly from theplane of the other portion of the compound, such as where the atoms areconformationally locked in a configuration out of plane of the rest ofthe compound. In some examples, a planarity disrupting moiety isreferred to herein as a Z group. In some cases when a compound disclosedherein contains multiple planarity disrupting moiety attachment sites(e.g., multiple Z groups), two planarity disrupting moieties cancomprise the same substructure; such a configuration may be referred toherein as Z and Z forming a ring. In some cases, a planarity disruptingmoiety is bonded to a quaternary center, which may be carbon or aheteroatom (e.g., Si or Ge). In some cases, a quaternary center can be acomponent of two separate but joined ring structures, also referred toas a spiro compound. The presence of a planarity disrupting moiety in acompound can impact bulk properties, such as a crystallographic packingefficiency or density, which can be evident from or influence othermolecular properties, such as vapor pressure, enthalpy of melting,enthalpy of fusion, enthalpy of sublimation, or yield throughpurification by sublimation. In examples, donor moieties, D, containingone or more planarity disrupting moieties may be referred to herein ascore disrupted moieties. Similarly, photoactive compounds comprisingdonor moieties, D, containing one or more planarity disrupting moietiesmay be referred to herein as core disrupted photoactive compounds.

A “π-bridging moiety” or a “pi-bridging moiety” refers to moiety orsubgroup of a compound providing extended conjugation of π- or,optionally, p-electrons and linking between different portions of thecompound by way of a bivalent structure. Extended conjugation may occurwhen bonds in a chemical compound are in an alternating configuration ofsingle-bonds and multiple-bonds (e.g., double- or triple-bonds). In somecases, extended conjugation may contribute additional electrons to anaromatic system.

The term “conformationally locked” refers to a configuration where atomsof a compound or group are in a bonded arrangement limiting freerotation or movement of components thereof. A conformationally lockedgroup may have a limited number of arrangement that atoms of the groupcan adopt. As one example, a spiro group may be conformationally lockedin that the atoms making up the two ring structures of the group are notable to freely rotate relative to one another; such a configurationcontrasts with a group where free rotation of sub-groups the group canoccur. Examples of groups that are not conformationally locked mayinclude some alkyl groups, such as a methyl group, an ethyl group, apropyl group, or a butyl group), where methyl groups (—CH₃), ethylgroups (—CH₂CH₃), or the like, can undergo rotation. In some cases,sterics may limit rotation of some groups. In some cases, aconformationally locked group that is in a configuration that is out ofplane of another component of the compound may not be able to bepositioned in the plane due to the bonding arrangement of atoms in theconformationally locked group.

As used herein, the terms visible transparency, visibly transparent, andthe like refer to an optical property of a material that exhibits anoverall absorption, average absorption, or maximum absorption in thevisible band of 0%-70%, such as less than or about 70%, less than orabout 65%, less than or about 60%, less than or about 55%, less than orabout 50%, less than or about 45%, less than or about 40%, less than orabout 35%, less than or about 30%, less than or about 25%, or less thanor about 20%. Stated another way, visibly transparent materials maytransmit 30%-100% of incident visible light, such as greater than orabout 80% of incident visible light, greater than or about 75% ofincident visible light, greater than or about 70% of incident visiblelight, greater than or about 65% of incident visible light, greater thanor about 60% of incident visible light, greater than or about 55% ofincident visible light, greater than or about 50% of incident visiblelight, greater than or about 45% of incident visible light, greater thanor about 40% of incident visible light, greater than or about 35% ofincident visible light, or greater than or about 30% of incident visiblelight. Visibly transparent materials are generally considered at leastpartially see-through (e.g., not completely opaque) when viewed by ahuman. Optionally, visibly transparent materials may be colorless (e.g.,not exhibiting strong visible absorption features that would provide anappearance of a particular color) when viewed by a human.

As used herein, the term “visible” refers to a band of electromagneticradiation for which the human eye is sensitive. For example, visiblelight may refer to light having wavelengths between about 450 nm andabout 650 nm.

The term “near-infrared” or “NIR” refers to a band of electromagneticradiation having wavelengths longer than those for which the human eyeis sensitive. For example, near-infrared light may refer to light havingwavelengths greater than 650 nm, such as between about 650 nm and about1400 nm or between about 650 nm and 2000 nm.

The term “ultraviolet” or “UV” refers to a band of electromagneticradiation having wavelengths shorter than those for which the human eyeis sensitive. For example, ultraviolet light may refer to light havingwavelengths less than 450 nm, such as between about 200 nm and about 450nm or between about 280 nm and 450 nm.

The disclosed compounds can be used in any application, though thespecific application described herein is for use as photoactivecompounds in an organic photovoltaic device, such as electron acceptorcompounds or electron donor compounds. In some examples, the disclosedcompounds are paired with a counterpart photoactive material (e.g., anelectron donor material or an electron acceptor material) to formheterojunction structures comprising an electron donor compound and acounterpart electron acceptor material or comprising an electronacceptor compound and a counterpart electron donor material, as furtherdescribed below, for use in generating and separating electron-holepairs for converting electromagnetic radiation (e.g., ultraviolet light,visible light, and/or near-infrared light) into useful electrical energy(e.g., voltage/current). In a specific example, the photovoltaic deviceincorporating one or more of the disclosed photoactive compounds is avisibly transparent photovoltaic device. In other examples, thephotovoltaic device incorporating one or more of the disclosedphotoactive compounds is a partially transparent photovoltaic device, acolored partially transparent photovoltaic device, or an opaquephotovoltaic device

FIG. 3A is a simplified schematic diagram illustrating a photovoltaicdevice according to some examples. As illustrated in FIG. 3A, thephotovoltaic device 300 includes a number of layers and elementsdiscussed more fully below. As discussed in relation to FIG. 4, thephotovoltaic device 300 may be visibly transparent, which indicates thatthe photovoltaic device absorbs optical energy at wavelengths outsidethe visible wavelength band of 450 nm to 650 nm, for example, whilesubstantially transmitting visible light inside the visible wavelengthband. As illustrated in FIG. 3A, UV and/or NIR light is absorbed in thelayers and elements of the photovoltaic device while visible light istransmitted through the device, though in some cases, such as in apartially transparent photovoltaic device or an opaque photovoltaicdevice, visible light may be absorbed, such as by a photoactive layer.

Substrate 305, which can be glass or other visibly transparent materialsproviding sufficient mechanical support to the other layers andstructures illustrated, supports optical layers 310 and 312. Theseoptical layers can provide a variety of optical properties, includingantireflection (AR) properties, wavelength selective reflection ordistributed Bragg reflection properties, index matching properties,encapsulation, or the like. Optical layers may advantageously be visiblytransparent. An additional optical layer 314 can be utilized, forexample, as an AR coating, an index matching later, a passive infraredor ultraviolet absorption layer, etc. Optionally, optical layers may betransparent to ultraviolet and/or near-infrared light or transparent toat least a subset of wavelengths in the ultraviolet and/or near-infraredbands. Depending on the configuration, additional optical layer 314 mayalso be a passive visible absorption layer or a neutral filter, forexample. Example substrate materials include various glasses and rigidor flexible polymers. Multilayer substrates may also be utilized.Substrates may have any suitable thickness to provide the mechanicalsupport needed for the other layers and structures, such as, forexample, thicknesses from 1 mm to 20 mm. In some cases, the substratemay be or comprise an adhesive film to allow application of thephotovoltaic device 300 to another structure, such as a window pane,display device, etc.

It will be appreciated that, although some of the devices describedherein exhibit visible transparency, photovoltaic devices are alsodisclosed herein that are not fully visibly transparent, as some of thephotoactive compounds described herein may exhibit visible absorption.In the case of a visibly transparent photovoltaic device that overallexhibits visible transparency, such as a transparency in the 450-650 nmrange greater than 30%, greater than 40%, greater than 50%, greater than60%, greater than 70%, or up to or approaching 100%, certain materialstaken individually may exhibit absorption in portions of the visiblespectrum. Optionally, each individual material or layer in a visiblytransparent photovoltaic device has a high transparency in the visiblerange, such as greater than 30% (e.g., between 30% and 100%). It will beappreciated that transmission or absorption may be expressed as apercentage and may be dependent on the material's absorbance properties,a thickness or path length through an absorbing material, and aconcentration of the absorbing material, such that a material with anabsorbance in the visible spectral region may still exhibit a lowabsorption or high transmission if the path length through the absorbingmaterial is short and/or the absorbing material is present in lowconcentration.

As described herein and below, various photoactive materials in variousphotoactive layers advantageously can exhibit minimal absorption in thevisible region (e.g., less than 20%, less than 30%, less than 40%, lessthan 50%, less than 60%, or less than 70%), and instead exhibit highabsorption in the near-infrared and/or ultraviolet regions (e.g., anabsorption peak of greater than 50%, greater than 60%, greater than 70%,or greater than 80%). For some applications, absorption in the visibleregion may be as large as 70%. Various configurations of othermaterials, such as the substrate, optical layers, and buffer layers, maybe useful for allowing these materials to provide overall visibletransparency, even though the materials may exhibit some amount ofvisible absorption. For example, a thin film of a metal may be includedin a transparent electrode, such as a metal that exhibits visibleabsorption, like Ag or Cu; when provided in a thin film configuration,however, the overall transparency of the film may be high. Similarly,materials included in an optical or buffer layer may exhibit absorptionin the visible range but may be provided at a concentration or thicknesswhere the overall amount of visible light absorption is low, providingvisible transparency.

The photovoltaic device 300 also includes a set of transparentelectrodes 320 and 322 with a photoactive layer 340 positioned betweenelectrodes 320 and 322. These electrodes, which can be fabricated usingITO, thin metal films, or other suitable visibly transparent materials,provide electrical connection to one or more of the various layersillustrated. For example, thin films of copper, silver, or other metalsmay be suitable for use as a visibly transparent electrode, even thoughthese metals may absorb light in the visible band. When provided as athin film, however, such as a film having a thickness of 1 nm to 200 nm(e.g., about 5 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm,about 30 nm, about 35 nm, about 40 nm, about 45 nm, about 50 nm, about55 nm, about 60 nm, about 65 nm, about 70 nm, about 75 nm, about 80 nm,about 85 nm, about 90 nm, about 95 nm, about 100 nm, about 105 nm, about110 nm, about 115 nm, about 120 nm, about 125 nm, about 130 nm, about135 nm, about 140 nm, about 145 nm, about 150 nm, about 155 nm, about160 nm, about 165 nm, about 170 nm, about 175 nm, about 180 nm, about185 nm, about 190 nm, or about 195 nm), an overall transmittance of thethin film in the visible band may remain high, such as greater than 30%,greater than 40%, greater than 50%, greater than 60%, greater than 70%,greater than 80%, or greater than 90%. Advantageously, thin metal films,when used as transparent electrodes, may exhibit lower absorption in theultraviolet band than other semiconducting materials that may be usefulas a transparent electrode, such as ITO, as some semiconductingtransparent conducting oxides exhibit a band gap that occurs in theultraviolet band and thus are highly absorbing or opaque to ultravioletlight. In some cases, however, an ultraviolet absorbing transparentelectrode may be used, such as to screen at least a portion of theultraviolet light from underlying components, as ultraviolet light maydegrade certain materials.

A variety of deposition techniques may be used to generate a transparentelectrode, including vacuum deposition techniques, such as atomic layerdeposition, chemical vapor deposition, physical vapor deposition, vacuumthermal evaporation, sputter deposition, epitaxy, etc. Solution-baseddeposition techniques, such as spin-coating, may also be used in somecases. In addition, various components, such as transparent electrodes,may be patterned using techniques known in the art of microfabrication,including lithography, lift off, etching, etc.

Buffer layers 330 and 332 and photoactive layer 340 are utilized toimplement the electrical and optical properties of the photovoltaicdevice. These layers can be layers of a single material or can includemultiple sub-layers as appropriate to the particular application. Thus,the term “layer” is not intended to denote a single layer of a singlematerial but can include multiple sub-layers of the same or differentmaterials. In some cases, layers may partially or completely overlap. Insome examples, buffer layer 330, photoactive layer(s) 340 and bufferlayer 332 are repeated in a stacked configuration to provide tandemdevice configurations, such as including multiple heterojunctions. Insome examples, the photoactive layer(s) include electron donor materialsand electron acceptor materials, also referred to as donors andacceptors. These donors and acceptors can, in some cases, be visiblytransparent, but absorb outside the visible wavelength band to providethe photoactive properties of the device. In the case of partiallytransparent and opaque photovoltaic devices, the donors and/or acceptorscan absorb in the visible region.

Useful buffer layers include those that function as electron transportlayers, electron blocking layers, hole transport layers, hole blockinglayers, exciton blocking layers, optical spacers, physical bufferlayers, charge recombination layers, or charge generation layers. Bufferlayers may exhibit any suitable thickness to provide the bufferingeffect desired and may optionally be present or absent. Useful bufferlayers, when present, may have thicknesses from 1 nm to 1 μm. Variousmaterials may be used as buffer layers, including fullerene materials,carbon nanotube materials, graphene materials, metal oxides, such asmolybdenum oxide, titanium oxide, zinc oxide, etc., polymers, such aspoly(3,4-ethylenedioxythiophene), polystyrene sulfonic acid,polyaniline, etc., copolymers, polymer mixtures, and small molecules,such as bathocuproine. Buffer layers may be applied using a depositionprocess (e.g., vacuum thermal evaporation) or a solution processingmethod (e.g., spin-coating).

FIG. 3B depicts an overview of various example single junctionconfigurations for photoactive layer 340. Photoactive layer 340 mayoptionally correspond to mixed donor/acceptor (bulk heterojunction)configurations, planar donor/acceptor configurations, planar and mixeddonor/acceptor configurations, or gradient donor/acceptorconfigurations. Various materials may be used as the photoactive layers340, such as visibly transparent materials that absorb in theultraviolet band or the near-infrared band but that only absorbminimally, if at all, in the visible band. In this way, the photoactivematerial may be used to generate electron-hole pairs for powering anexternal circuit by way of ultraviolet and/or near-infrared absorption,leaving the visible light relatively unperturbed to provide visibletransparency. In other cases, however, photoactive layers 340 mayinclude materials that absorb in the visible region. As illustrated,photoactive layer 340 may comprise a planar heterojunction includingseparate donor and acceptor layers. Photoactive layer 340 mayalternatively comprise a planar-mixed heterojunction structure includingseparate acceptor and donor layers and a mixed donor-acceptor layer.Photoactive layers 340 may alternatively comprise a mixed heterojunctionstructure including a fully mixed acceptor-donor layer or thoseincluding a mixed donor-acceptor layer with various relativeconcentration gradients.

Photoactive layers 340 may have any suitable thickness and may have anysuitable concentration or composition of photoactive materials toprovide a desired level of transparency and ultraviolet/near-infraredabsorption characteristics. Example thicknesses of a photoactive layermay range from about 1 nm to about 1 μm, about 1 nm to about 300 nm, orabout 1 nm to about 100 nm. In some cases, photoactive layers 340 may bemade up of individual sub-layers or mixtures of layers to providesuitable photovoltaic power generation characteristics, as illustratedin FIG. 3B. The various configurations depicted in FIG. 3B may be usedand dependent on the particular donor and acceptor materials used inorder to provide advantageous photovoltaic power generation. Forexample, some donor and acceptor combinations may benefit fromparticular configurations, while other donor and acceptor combinationsmay benefit from other particular configurations. Donor materials andacceptor materials may be provided in any ratio or concentration toprovide suitable photovoltaic power generation characteristics. Formixed layers, the relative concentration of donors to acceptors isoptionally between about 20 to 1 and about 1 to 20. Optionally, therelative concentration of donors to acceptors is optionally betweenabout 5 to 1 and about 1 to 5. Optionally, donors and acceptors arepresent in a 1 to 1 ratio.

It will be appreciated that, in various examples, photovoltaic device300 comprises transparent electrode 320, photoactive layer(s) 340, andtransparent electrode 322, and that any one or more of substrate 305,optical layers 310, 312, and 314, and/or buffer layers 330 and 332 maybe optionally included or excluded.

As described more fully herein, disclosed examples can employphotoactive compounds for one or more of the buffer layers, opticallayers, and/or the photoactive layers. These compounds can includesuitably functionalized versions for modification of the electricaland/or optical properties of the core structure. As an example, thedisclosed compounds can include functional groups that decrease theabsorption properties in the visible wavelength band between 450 nm to650 nm and increase the absorption properties in the NIR band atwavelengths greater than 650 nm.

As an example, the disclosed photoactive compounds are useful as anelectron acceptor materials or electron donor materials and may bepaired with suitable counterpart materials of the opposite character,such as counterpart electron donor materials or counterpart electronacceptor materials, in order to provide a useful heterojunction-basedphotoactive layer in the photovoltaic device. Example electron donorphotoactive materials or electron acceptor photoactive materials may bevisibly transparent. In cases of partially transparent or opaquephotovoltaic devices, the photoactive materials can absorb light in thevisible region.

In examples, the chemical structure of the photoactive compounds can befunctionalized with one or more directing groups, such as electrondonating groups, electron withdrawing groups, or substitutions about orto a core metal atom or group, in order to provide desirable electricalcharacteristics to the material. For example, in some examples, thephotoactive compounds are functionalized with amine groups, phenolgroups, alkyl groups, phenyl groups, or other electron donating groupsto improve the ability of the material to function as an electron donorin a photovoltaic device. As another example, the photoactive compoundsmay be functionalized with cyano groups, halogens, sulfonyl groups, orother electron withdrawing groups to improve the ability of the materialto function as an electron acceptor in a photovoltaic device.

In examples, the photoactive compounds are functionalized to providedesirable optical characteristics. For example, the photoactivecompounds may be functionalized with an extended conjugation to redshiftthe absorption profile of the material. It will be appreciated thatconjugation may refer to a delocalization of pi electrons in a moleculeand may be characterized by alternating single and multiple bonds in amolecular chemical structure, and/or the presence of aromaticstructures. For example, functionalizations that extend the electronconjugation may include fusing one or more aromatic groups to themolecular structure of the material. Other functionalizations that mayprovide extended conjugation include alkene functionalization, such asby a vinyl group, aromatic or heteroaromatic functionalization, carbonylfunctionalization, such as by an acyl group, sulfonyl functionalization,nitro functionalization, cyano functionalization, etc. It will beappreciated that various molecular functionalizations may impact boththe optical and the electrical properties of the photoactive compounds.

It will be appreciated that device function may be impacted by themorphology of the active layers in the solid state. Separation ofelectron donors and acceptors into discrete domains, with dimensions onthe scale of the exciton diffusion length and large interfacial areas,can be advantageous for achieving high device efficiency.Advantageously, the molecular framework of the photoactive materials canbe tailored to control the morphology of the materials. For example, theintroduction of functional groups as described herein can have largeimpacts to the morphology of the material in the solid state, regardlessof whether such modifications impact the energetics or electronicproperties of the material. Such morphological variations can beobserved in pure materials and when a particular material is blendedwith a corresponding donor or acceptor. Useful functionalities tocontrol morphology include, but are not limited to, addition of alkylchains, conjugated linkers, fluorinated alkanes, bulky groups (e.g.,tert-butyl, phenyl, naphthyl or cyclohexyl), as well as more complexcoupling procedures designed to force parts of the structure out of theplane of the molecule to inhibit excessive crystallization.

In examples, other molecular structural characteristics may providedesirable electrical and optical properties in the photoactivecompounds. For example, the photoactive compounds may exhibit portionsof the molecule that may be characterized as electron donating whileother portions of the molecule may be characterized as electronaccepting. Without wishing to be bound by any theory, moleculesincluding alternating electron donating and electron accepting portionsmay result in redshifting the absorption characteristics of the moleculeas compared to similar molecules lacking alternating electron donatingand electron accepting portions. For example, alternating electrondonating and electron accepting portions may decrease or otherwiseresult in a lower energy gap between a highest occupied molecularorbital and a lowest unoccupied molecular orbital. Organic donor and/oracceptor groups may be useful as R-group substituents, such as on anyaryl, aromatic, heteroaryl, heteroaromatic, alkyl, or alkenyl group, inthe visibly transparent photoactive compounds described herein. Exampleacceptor and donor groups are described below in more detail.

In examples, the photoactive compounds may exhibit symmetric structures,such as structures having two or more points of symmetry. Symmetricstructures may include those where a core group is functionalized onopposite sides by the same groups, or where two of the same core groupsare fused or otherwise bonded to one another. In other examples, thephotoactive compounds may exhibit asymmetric structures, such asstructures having fewer than two points of symmetry. Asymmetricstructures may include those where a core group is functionalized onopposite sides by different groups or where two different core groupsare fused or otherwise bonded to one another.

When the materials described herein are incorporated as a photoactivelayer in a photovoltaic device, for example as an electron acceptor oran electron donor, the layer thicknesses can be controlled to varydevice output, absorbance, or transmittance. For example, increasing thedonor or acceptor layer thickness can increase the light absorption inthat layer. In some cases, increasing a concentration of donor/acceptormaterials in a donor or acceptor layer may similarly increase the lightabsorption in that layer. However, in some examples, a concentration ofdonor/acceptor materials may not be adjustable, such as when activematerial layers comprise pure or substantially pure layers ofdonor/acceptor materials or pure or substantially pure mixtures ofdonor/acceptor materials. Optionally, donor/acceptor materials may beprovided in a solvent or suspended in a carrier, such as a buffer layermaterial, in which case the concentration of donor/acceptor materialsmay be adjusted. In some examples, the donor layer concentration isselected where the current produced is maximized. In some examples, theacceptor layer concentration is selected where the current produced ismaximized.

However, the charge collection efficiency can decrease with increasingdonor or acceptor thickness due to the increased “travel distance” forthe charge carriers. Therefore, there may be a trade-off betweenincreased absorption and decreasing charge collection efficiency withincreasing layer thickness. It can thus be advantageous to selectmaterials as described herein that have a high absorption coefficientand/or concentration to allow for increased light absorption perthickness. In some examples, the donor layer thickness is selected wherethe current produced is maximized. In some examples, the acceptor layerthickness is selected where the current produced is maximized.

In addition to the individual photoactive layer thicknesses formed frommaterials described herein, the thickness and composition of the otherlayers in the transparent photovoltaic device can also be selected toenhance absorption within the photoactive layers. The other layers(buffer layers, electrodes, etc.), are typically selected based on theiroptical properties (index of refraction and extinction coefficient) inthe context of the thin film device stack and resulting optical cavity.For example, a near-infrared absorbing photoactive layer can bepositioned in the peak of the optical field for the near-infraredwavelengths where it absorbs to maximize absorption and resultingcurrent produced by the device. This can be accomplished by spacing thephotoactive layer at an appropriate distance from the electrode using asecond photoactive layer and/or optical layers as spacer. A similarscheme can be used for ultraviolet or visible absorbing photoactivelayers. In many cases, the peaks of the longer wavelength optical fieldswill be positioned further from the more reflective of the twotransparent electrodes compared to the peaks of the shorter wavelengthoptical fields. Thus, when using separate donor and acceptor photoactivelayers, the donor and acceptor can be selected to position the more redabsorbing (longer wavelength) material further from the more reflectiveelectrode and the more blue absorbing (shorter wavelength) closer to themore reflective electrode.

In some examples, optical layers may be included to increase theintensity of the optical field at wavelengths where the donor absorbs inthe donor layer to increase light absorption and hence, increase thecurrent produced by the donor layer. In some examples, optical layersmay be included to increase the intensity of the optical field atwavelengths where the acceptor absorbs in the acceptor layer to increaselight absorption and hence, increase the current produced by theacceptor layer. In some examples, optical layers may be used to improvethe transparency of the stack by either decreasing visible absorption orvisible reflection. Further, the electrode material and thickness may beselected to enhance absorption outside the visible range within thephotoactive layers, while preferentially transmitting light within thevisible range.

Optionally, enhancing spectral coverage of a photovoltaic device isachieved by the use of a multi-cell series stack of photovoltaicdevices, referred to as tandem cells, which may be included as multiplestacked instances of buffer layer 330, photoactive layer 340, and bufferlayer 332, as described with reference to FIG. 3A. This architectureincludes more than one photoactive layer, which are typically separatedby a combination of buffer layer(s) and/or thin metal layers, forexample. In this architecture, the currents generated in each subcellflow in series to the opposing electrodes and therefore, the net currentin the cell is limited by the smallest current generated by a particularsubcell, for example. The open circuit voltage (VOC) is equal to the sumof the VOCs of the subcells. By combining sub-cells fabricated withdifferent donor-acceptors pairs which absorb in different regions of thesolar spectrum, a significant improvement in efficiency relative to asingle junction cell can be achieved.

Additional description related to the materials utilized in one or moreof the buffer layers and the photoactive layers, including donor layersand/or acceptor layers, are provided below.

FIG. 4 is simplified plot illustrating the solar spectrum, human eyesensitivity, and exemplary visibly transparent photovoltaic deviceabsorption as a function of wavelength. As illustrated in FIG. 4,examples of visibly transparent photovoltaic devices can utilizephotovoltaic structures that have low absorption in the visiblewavelength band between about 450 nm and about 650 nm but absorb in theUV and NIR bands, e.g., outside the visible wavelength band, enablingvisibly transparent photovoltaic operation. The ultraviolet band orultraviolet region may be described, in examples, as wavelengths oflight of between about 200 nm and 450 nm. It will be appreciated thatuseful solar radiation at ground level may have limited amounts ofultraviolet less than about 280 nm and, thus, the ultraviolet band orultraviolet region may be described as wavelengths of light of betweenabout 280 nm and 450 nm, in some examples. The near-infrared band ornear-infrared region may be described, in examples, as wavelengths oflight of between about 650 nm and 1400 nm. Various compositionsdescribed herein may exhibit absorption including a NIR peak with amaximum absorption strength in the visible region that is smaller thanthat in the NIR region.

FIG. 5 provides a schematic energy level diagram overview for operationof an example organic photovoltaic device, such as visibly transparentphotovoltaic device 300. For example, in such a photovoltaic device,various photoactive materials may exhibit electron donor or electronacceptor characteristics, depending on their properties and the types ofmaterials that are used for buffer layers, counterpart materials,electrodes, etc. As depicted in FIG. 5, each of the donor and acceptormaterials have a highest occupied molecular orbital (HOMO) and a lowestunoccupied molecular orbital (LUMO). A transition of an electron fromthe HOMO to the LUMO may be imparted by absorption of photons. Theenergy between the HOMO and the LUMO (the HOMO-LUMO gap) of a materialrepresents approximately the energy of the optical band gap of thematerial. For the electron donor and electron acceptor materials usefulwith the transparent photovoltaic devices provided herein, the HOMO-LUMOgap for the electron donor and electron acceptor materials preferablyfalls outside the energy of photons in the visible range. For example,the HOMO-LUMO gap may be in the ultraviolet region or the near-infraredregion, depending on the photoactive materials. In some cases, theHOMO-LUMO gap may be in the visible region or overlap with the visibleregion and the ultraviolet region or overlap with the visible region andthe near-infrared region, such as for partially transparent or opaquephotovoltaic devices. It will be appreciated that the HOMO is comparableto the valence band in conventional conductors or semiconductors, whilethe LUMO is comparable to the conduction band in conventional conductorsor semiconductors.

The narrow absorption spectrum of many organic molecules, such asorganic semiconductors, can make it difficult to absorb the entireabsorption spectra using a single molecular species. Therefore, electrondonor and acceptor molecules are generally paired to afford acomplementary absorption spectrum and increase spectral coverage oflight absorption. Additionally, the donor and acceptor molecules areselected such that their energy levels (HOMO and LUMO) lie favorablywith respect to one another. The difference in the LUMO level of donorand acceptor provides a driving force for dissociation of electron-holepairs (excitons) created on the donor whereas the difference in the HOMOlevels of donor and acceptors provides driving force for dissociation ofelectron-hole pairs (excitons) created on the acceptor. In someexamples, it may be useful for the acceptor to have high electronmobility to efficiently transport electrons to an adjacent buffer layer.In some examples, it may be useful for the donor to have high holemobility to efficiently transport holes to the buffer layer.Additionally, in some examples, it may be useful to increase thedifference in the LUMO level of the acceptor and the HOMO level of thedonor to increase the open circuit voltage (VOC), since VOC has beenshown to be directly proportional to the difference between LUMO of theacceptor and HOMO of the donor. Such donor-acceptor pairings within thephotoactive layer may be accomplished by appropriately pairing one ofthe materials described herein with a complementary material, whichcould be a different photoactive compound described herein or acompletely separate material system.

The buffer layer adjacent to the donor, generally referred to as theanode buffer layer or hole transport layer, is selected such that HOMOlevel or valence band (in the case of inorganic materials) of the bufferlayer is aligned in the energy landscape with the HOMO level of thedonor to transport holes from the donor to the anode (transparentelectrode). In some examples, it may be useful for the buffer layer tohave high hole mobility. The buffer layer adjacent to the acceptor,generally referred to as the cathode buffer layer or electron transportlayer, is selected such that LUMO level or conduction band (in the caseof inorganic materials) of the buffer layer is aligned in the energylandscape with the LUMO level of the acceptor to transport electronsfrom the acceptor to the cathode (transparent electrode). In someexamples, it may be useful for the buffer layer to have high electronmobility.

FIG. 6A, FIG. 6B, FIG. 6C, and FIG. 6D provide plots showing exampleabsorption bands for different electron donor and electron acceptorconfigurations useful with visibly transparent photovoltaic devices. InFIG. 6A, the donor material exhibits absorption in the NIR, while theacceptor material exhibits absorption in the UV. FIG. 6B depicts theopposite configuration, where the donor material exhibits absorption inthe UV, while the acceptor material exhibits absorption in the NIR.

FIG. 6C depicts an additional configuration, where both the donor andacceptor materials exhibit absorption in the NIR. As illustrated in thefigures, the solar spectrum exhibits significant amounts of usefulradiation in the NIR with only relatively minor amounts in theultraviolet, making the configuration depicted in FIG. 6C useful forcapturing a large amount of energy from the solar spectrum. It will beappreciated that other examples are contemplated where both the donorand acceptor materials exhibit absorption in the NIR, such as depictedin FIG. 6D where the acceptor is blue shifted relative to the donor,opposite the configuration depicted in FIG. 6C, where the donor is blueshifted relative to the acceptor.

The present disclosure also provides methods for making photovoltaicdevices, such as photovoltaic device 300. For example, FIG. 7 providesan overview of a method 700 for making a photovoltaic device inaccordance with some examples. Method 700 begins at block 705, where atransparent substrate is provided. It will be appreciated that usefultransparent substrates include visibly transparent substrates, such asglass, plastic, quartz, and the like. Flexible and rigid substrates areuseful with various examples. Optionally, the transparent substrate isprovided with one or more optical layers preformed on top and/or bottomsurfaces.

At block 710, one or more optical layers are optionally formed on orover the transparent substrate, such as on top and/or bottom surfaces ofthe transparent substrate. Optionally, the one or more optical layersare formed on other materials, such as an intervening layer or material,such as a transparent conductor. Optionally, the one or more opticallayers are positioned adjacent to and/or in contact with the visiblytransparent substrate. It will be appreciated that formation of opticallayers is optional, and some examples may not include optical layersadjacent to and/or in contact with the transparent substrate. Opticallayers may be formed using a variety of methods including, but notlimited to, one or more chemical deposition methods, such as plating,chemical solution deposition, spin coating, dip coating, chemical vapordeposition, plasma enhanced chemical vapor deposition, and atomic layerdeposition, or one or more physical deposition methods, such as vacuumthermal evaporation, electron beam evaporation, molecular beam epitaxy,sputtering, pulsed laser deposition, ion beam deposition, andelectrospray deposition. It will be appreciated that useful opticallayers include visibly transparent optical layers. Useful optical layersinclude those that provide one or more optical properties including, forexample, antireflection properties, wavelength selective reflection ordistributed Bragg reflection properties, index matching properties,encapsulation, or the like. Useful optical layers may optionally includeoptical layers that are transparent to ultraviolet and/or near-infraredlight. Depending on the configuration, however, some optical layers mayoptionally provide passive infrared and/or ultraviolet absorption.Optionally, an optical layer may include a visibly transparentphotoactive compound described herein.

At block 715, a transparent electrode is formed. As described above, thetransparent electrode may correspond to an indium tin oxide thin film orother transparent conducting film, such as thin metal films (e.g., Ag,Cu, etc.), multilayer stacks comprising thin metal films (e.g., Ag, Cu,etc.) and dielectric materials, or conductive organic materials (e.g.,conducting polymers, etc.). It will be appreciated that transparentelectrodes include visibly transparent electrodes. Transparentelectrodes may be formed using one or more deposition processes,including vacuum deposition techniques, such as atomic layer deposition,chemical vapor deposition, physical vapor deposition, vacuum thermalevaporation, sputter deposition, epitaxy, etc. Solution based depositiontechniques, such as spin-coating, may also be used in some cases. Inaddition, transparent electrodes may be patterned by way ofmicrofabrication techniques, such as lithography, lift off, etching,etc.

At block 720, one or more buffer layers are optionally formed, such ason the transparent electrode. Buffer layers may be formed using avariety of methods including, but not limited to, one or more chemicaldeposition methods, such as a plating, chemical solution deposition,spin coating, dip coating, chemical vapor deposition, plasma enhancedchemical vapor deposition, and atomic layer deposition, or one or morephysical deposition methods, such as vacuum thermal evaporation,electron beam evaporation, molecular beam epitaxy, sputtering, pulsedlaser deposition, ion beam deposition, and electrospray deposition. Itwill be appreciated that useful buffer layers include visiblytransparent buffer layers. Useful buffer layers include those thatfunction as electron transport layers, electron blocking layers, holetransport layers, hole blocking layers, optical spacers, physical bufferlayers, charge recombination layers, or charge generation layers. Insome cases, the disclosed visibly transparent photoactive compounds maybe useful as a buffer layer material. For example, a buffer layer mayoptionally include a visibly transparent photoactive compound describedherein.

At block 725, one or more photoactive layers are formed, such as on abuffer layer or on a transparent electrode. As described above,photoactive layers may comprise electron acceptor layers and electrondonor layers or co-deposited layers of electron donors and acceptors.Useful photoactive layers include those comprising the photoactivecompounds described herein. Photoactive layers may be formed using avariety of methods including, but not limited to, one or more chemicaldeposition methods, such as a plating, chemical solution deposition,spin coating, dip coating, chemical vapor deposition, plasma enhancedchemical vapor deposition, and atomic layer deposition, or one or morephysical deposition methods, such as vacuum thermal evaporation,electron beam evaporation, molecular beam epitaxy, sputtering, pulsedlaser deposition, ion beam deposition, and electrospray deposition.

In some examples, photoactive compounds useful for photoactive layersmay be deposited using a vacuum deposition technique, such as vacuumthermal evaporation. Vacuum deposition may take place in a vacuumchamber, such as at pressures of between about 10⁻⁵ Torr and about 10⁻⁸Torr. In one example, vacuum deposition may take place at a pressure ofabout 10⁻⁷ Torr. As noted above, various deposition techniques may beapplied. In some examples, thermal evaporation is used. Thermalevaporation may include heating a source of the material (e.g., thevisibly transparent photoactive compound) to be deposited to atemperature of between 150° C. and 500° C. The temperature of the sourceof material may be selected so as to achieve a thin film growth rate ofbetween about 0.01 nm/s and about 1 nm/s. For example, a thin filmgrowth rate of 0.1 nm/s may be used. These growth rates are useful togenerate thin films having thicknesses of between about 1 nm and 500 nmover the course of minutes to hours. It will be appreciated that variousproperties (e.g., the molecular weight, volatility, thermal stability)of the material being deposited may dictate or influence the sourcetemperature or maximum useful source temperature. For example, a thermaldecomposition temperature of the material being deposited may limit themaximum temperature of the source. As another example, a material beingdeposited that is highly volatile may require a lower source temperatureto achieve a target deposition rate as compared to a material that isless volatile, where a higher source temperature may be needed toachieve the target deposition rate. As the material being deposited isevaporated from the source, it may be deposited on a surface (e.g.,substrate, optical layer, transparent electrode, buffer layer, etc.) ata lower temperature. For example the surface may have a temperature fromabout 10° C. to about 100° C. In some cases, the temperature of thesurface may be actively controlled. In some cases, the temperature ofthe surface may not be actively controlled.

At block 730, one or more buffer layers are optionally formed, such ason the photoactive layer. The buffer layers formed at block 730 may beformed similar to those formed at block 720. It will be appreciated thatblocks 720, 725, and 730 may be repeated one or more times, such as toform a multilayer stack of materials including a photoactive layer and,optionally, various buffer layers.

At block 735, a second transparent electrode is formed, such as on abuffer layer or on a photoactive layer. Second transparent electrode maybe formed using techniques applicable to formation of first transparentelectrode at block 715.

At block 740, one or more additional optical layers are optionallyformed, such as on the second transparent electrode.

It should be appreciated that the specific steps illustrated in FIG. 7provide a particular method of making a photovoltaic device according tovarious examples. Other sequences of steps may also be performedaccording to alternative examples. For example, alternative examples mayperform the steps outlined above in a different order. Moreover, theindividual steps illustrated in FIG. 7 may include multiple sub-stepsthat may be performed in various sequences as appropriate to theindividual step. Furthermore, additional steps may be added or removeddepending on the particular applications. It will be appreciated thatmany variations, modifications, and alternatives may be used.

Method 700 may optionally be extended to correspond to a method forgenerating electrical energy. For example, a method for generatingelectrical energy may comprise providing a photovoltaic device, such asby making a photovoltaic device according to method 700. Methods forgenerating electrical energy may further comprise exposing thephotovoltaic device to visible, ultraviolet and/or near-infrared lightto drive the formation and separation of electron-hole pairs, asdescribed above with reference to FIG. 5, for example, for generation ofelectrical energy. The photovoltaic device may include the photoactivecompounds described herein as photoactive materials, buffer materials,and/or optical layers.

Turning now to further details on photoactive compounds, in someexamples, the photoactive compounds described herein comprises amolecular composition having a structure A-D-A, A-pi-D-A, A-pi-D-pi-A,A-D, or A-pi-D, wherein each “A” moiety is an electron acceptor moiety,the “D” moiety is an electron donor moiety, and the “pi” moiety is aπ-bridging moiety. Advantageously, the photoactive compounds can havemolecular weights making them suitable for physical vapor depositiontechniques, such as molecular weights from 200 amu to 1200 amu, forexample, such as from 200 amu to 900 amu, from 200 amu to 950 amu, from200 amu to 1000 amu, from 200 amu to 1050 amu, from 200 amu to 1100 amu.The photoactive compounds can exhibit thermal decomposition temperaturesfrom 150° C. to 500° C. or greater than 500° C. and/or sublimationtemperatures of 150° C. to 450° C. at pressures from 0.2 Torr to 10⁻⁷Torr. These characteristics can aid or impart stability making thephotoactive compounds suitable for use in physical vapor depositionprocesses.

The photoactive compounds can exhibit optical properties, as describedabove, such as where the photoactive compound exhibits absorption in theultraviolet, visible, and/or infrared regions. In some cases, thecompounds exhibit a bandgap of from 0.5 eV to 4.0 eV. For visiblytransparent photoactive compounds, the bandgap may be from 0.5 eV to 1.9eV or from 2.7 eV to 4.0 eV.

Each of the different A, pi, and D moieties in the photoactive compoundscan impact the absorption profile and the volatility. Withoutlimitation, each “A” moiety in a photoactive compound can beindependently selected from:

where each R is independently H, F, Cl, Br, I, CH₃, CF₃, or CN, whereeach Y¹ is independently C(CN)₂, O, S, or cyanoimine (N—CN), where eachY² is independently CH or N or Y² is not present and the A moiety isconnected to the D or pi moiety by a double bond, where each X^(i) isindependently O, S, Se, or C1-C8 alkylated N (e.g., NR^(N) or NR^(O),such as where R^(N) is a C1-C8 alkyl group), and where each R³ is CN orC(CN)₂, and where R^(O) is a branched or straight chain C1-C8 alkylgroup, such as having a molecular weight of from 15 amu to 100 amu. Insome examples, a Y² not being present in an A moiety indicates that the

portion of the A moiety comprises

where the double bond connects to a pi moiety, such as when pi comprises

In some cases, it may be desirable for at least one Y¹ in a photoactivecompound to be O or S, and not C(CN)₂. Although use of O instead ofC(CN)₂ as a Y¹ in an A moiety can reduce a molecular weight by about 48amu, the resultant photoactive compounds can exhibit larger increases invapor pressure and volatility than are expected for just this change inmolecular weight. Similarly, the use of S instead of C(CN)₂ as a Y¹ inan A moiety can reduce a molecular weight by about 32 amu, but theresultant photoactive compounds can exhibit larger increases in vaporpressure and volatility than are expected for just this change inmolecular weight.

In some cases, it may be desirable for at least one Y² in a photoactivecompound to be N, and not CH or a double-bond linkage. Such A moietiesmay be referred to as having a structure of

where A′ is an imine-linked electron acceptor moiety, which may be orcomprise a heterocycle, which may be substituted or unsubstituted. Insome examples, A may be an imine-linked indandione, an imine-linkeddicyanomethyleneindanone, an imine-linked bis(dicyanomethylidene)indan,or an imine-linked dicyanovinylene. Use of N as a Y² instead of CH or adouble-bond linkage can result in an increase in molecular weight byabout 1 amu, but other properties can change, also. For example, use ofN as a Y² instead of CH or a double-bond linkage can result in a changein the optical properties of the photoactive compound. As one example, aredshift in the absorption maximum, such as by 50-100 nm can be achievedby using imine-linking between the A moiety and the D moiety or a pimoiety. In another example, a decrease in the band gap can be achieved,such as by about 0.25 eV to 0.75 eV, by using imine-linking between theA moiety and the D moiety or a pi moiety.

Without limitation, each “pi” moiety in a photoactive compound can beindependently selected from:

where each X¹ is independently O, S, Se, or C1-C8 alkylated N (e.g.,NR^(N) or NR^(O), such as where R) is a C1-C8 alkyl group), each R isindependently H, F, Cl, Br, I, CH₃, CF₃, or CN, each W is independentlyH, F, or a branched or straight chain C1-C8 alkyl group or a branched orstraight chain C1-C8 alkoxy group, and each R^(N) is independently abranched, cyclic, or straight chain alkyl or ester group having amolecular weight of from 15 amu to 100 amu. In other examples, longerconjugated pi systems can be used, such as where one or more carbonchains containing alternating double and single bonds are included atthe position of the wavy line in the structures shown. In otherexamples, longer fused ring systems can be used, such as containing 3,4, or 5 fused 5-membered rings, such as

where each X² is independently O, S, Se, NH, NR^(N), CH₂, or C(R^(N))₂and each W is independently H, F, or a branched or straight chain C1-C8alkyl group or a branched or straight chain C1-C8 alkoxy group.Including pi moieties in the photoactive compounds can, for example,result in a change in optical properties of the photoactive compound. Asone example, a redshift in the absorption maximum can be achieved bylonger and longer pi moieties between the A moiety and the D moiety. Itwill be appreciated, however, that inclusion of a pi moiety in aphotoactive compound can result in an increase in the molecular weightof the compound, as compared to a compound comprising the same A and Dmoieties but not including a pi moiety. As one example, a pi moietycomprising a single 5-membered ring where X² is N can add about 64 amuto the molecular weight. For each additional fused 5-membered ring whereX² is N, about 38 amu more will be added to the molecular weight. Forexample, a pi moiety comprising two fused 5-membered rings where X² is Ncan add about 102 amu to the molecular weight. In some cases, theredshifted absorption maximum can be beneficial despite the increase inthe molecular weight and the associated reduction in vapor pressure andvolatility. In other cases, the redshifted absorption maximum may notoffset the increase in the molecular weight and the associated reductionin vapor pressure and volatility.

Without limitation, each “D” moiety in a photoactive compound can beindependently selected from:

where each X is independently O, S, Se, NH, NR^(N), CH₂, C(R^(N))₂,Si(R^(N))₂, or Ge(R^(N))₂, each R^(N) is independently a branched,cyclic, or straight chain alkyl or ester group having a molecular weightof from 15 amu to 100 amu, each W is independently H, F, or a branchedor straight chain C1-C8 alkyl group or a branched or straight chainC1-C8 alkoxy group, each R is independently H, F, Cl, Br, I, CH₃, CF₃,or CN, each Z is independently a side group, such as R^(N), or aplanarity disrupting moiety, Y³ is independently O or S, and Y⁴ isindependently CH, N, or CR.

A variety of side groups Z can be used. In some examples, one or more Zsare independently a substituted (e.g., halogen substituted) orunsubstituted alkyl group, a substituted (e.g., halogen substituted) orunsubstituted alkenyl group, an unsubstituted or methyl, ethyl, halogen,or trihalomethyl substituted cycloalkyl group, an unsubstituted ormethyl, ethyl, halogen, or trihalomethyl substituted cycloalkenyl group,an unsubstituted or methyl, ethyl, halogen, or trihalomethyl substitutedcyclopentadienyl group, or an unsubstituted or methyl, ethyl, halogen,or trihalomethyl substituted phenyl group. Optionally, Z contains one ormore halogen or trihalomethyl substituents. Optionally, two Zs togetherform an unsubstituted or methyl, ethyl, halogen, or trihalomethylsubstituted cycloalkyl group, an unsubstituted or methyl, ethyl,halogen, or trihalomethyl substituted cycloalkenyl group, anunsubstituted or methyl, ethyl, halogen, or trihalomethyl substitutedcyclopentadienyl group, or an unsubstituted or methyl, ethyl, halogen,or trihalomethyl substituted phenyl group. In some examples, two Zstogether form a group containing fused 5-membered rings that areunsubstituted or methyl, ethyl, halogen, or trihalomethyl substituted,fused 6-membered rings that are unsubstituted or methyl, ethyl, halogen,or trihalomethyl substituted, or fused 5-membered and 6-membered ringsthat are unsubstituted or methyl, ethyl, halogen, or trihalomethylsubstituted. In some examples, two Zs together form a heterocyclic groupor fused heterocyclic group. Optionally, one or more Z may be a hydrogenatom. Optionally, one or more Z may be 2-methylbutyl.

In some cases, each D moiety can include a planar central core with oneor more side groups Z. In the examples given above, each D moiety maycontain a planar fused ring central core structure comprising anaromatic, heteroaromatic, polycyclic aromatic, or polycyclicheteroaromatic moiety containing one or more 5-membered and/or6-membered rings in which the ring structure comprises carbon andoptionally one or more heteroatoms. In some cases, the atom that one ormore side groups Z are bonded to is a quaternary center, Q. For example,the D moiety may comprise

wherein Q is a quaternary center, which may be C, Si, or Ge, forexample. The presence of a quaternary center may be useful forconformationally locking the one or more side groups Z in aconfiguration where they are positioned out of plane to the centralcore. In specific examples, a D moiety may comprise one or more of thefollowing groups or a heterocyclic analog thereof:

each of which is unsubstituted or substituted with one or more methyl,ethyl, halogen (e.g. fluoro), or trihalomethyl (e.g., trifluoromethyl)groups, or heterocyclic analogs thereof. Although a single configurationis shown for various different sized alkene rings in these examples,isomers where the double bond is in a different position are alsocontemplated herein, such as

optionally substituted with one or more methyl, ethyl, halogen (e.g.fluoro), or trihalomethyl (e.g., trifluoromethyl) groups, orheterocyclic analogs thereof. Inclusion of side groups comprising a ringgroup containing a quaternary carbon atom Q, as shown, may allow theelectron donor molecule to exhibit a spiro structure.

Inclusion of a side group (or groups) Z that is conformationally lockedout of plane to the central core may provide advantageous properties tothe photoactive compound, such as an increase in the sublimation yield.For example, photoactive compounds containing side groups that areconformationally locked out of plane to the central core (e.g., coredisrupted photoactive compounds) may exhibit larger vapor pressures andlower sublimation temperatures as compared to other compounds containingside groups that are not conformationally locked out of plane to thecentral core (e.g., photoactive compounds lacking core disruption), suchas despite exhibiting the same, nearly the same, or comparable molecularweights (e.g., within 2 or 3 amu of one another). Without wishing to bebound by any theory, inclusion of side groups that are conformationallylocked out of plane to the central core of a photoactive compound canresult in disrupting the bulk crystal packing efficiency of thephotoactive compound, making the crystallized structure lessenergetically favorable than photoactive compounds with more tightlypacked crystal structures. In this way, the core disrupted photoactivecompounds may exhibit relatively smaller heats of fusion, evaporation,and/or sublimation, making it relatively easier to evaporate thesecompounds into the gas phase. As such, the sublimation yield of aphotoactive compound including side groups that are conformationallylocked out of plane to the central core may be greater than that of asimilar photoactive compound with side groups that are notconformationally locked out of plane to the central core.

A variety of different photoactive compounds can be formulated and usedaccording to the above description. Some specific example photoactivecompounds include those having a formula of:

It will be appreciated that a variety of other photoactive compoundscomprising various combinations of the disclosed A, D, and pi moietiesare also contemplated.

For example, additional photoactive compounds include those having anyof the following formulas, such as where any indicated Z groups areoptionally 2-methylbutyl:

The disclosed photoactive compounds can be paired with a variety ofother compounds to form a photovoltaic heterojunction. For example, whenthe photoactive compound is an electron acceptor compound, it can bepaired with a counterpart electron donor material. As another example,when the photoactive compound is an electron donor compound, it can bepaired with a counterpart electron acceptor material. A counterpartelectron donor material may be a counterpart electron donor compound,for example, and may be different in some cases from the photoactivematerials described herein. A counterpart electron acceptor material maybe a counterpart electron donor compound, for example, and may bedifferent in some cases from the photoactive materials described herein.In some cases, a photoactive layer may comprise one or multipledifferent electron donor compounds (e.g., blends of differentphotoactive compounds). In some cases, a photoactive layer may compriseone or multiple different electron acceptor compounds (e.g., blends ofdifferent photoactive compounds).

In some examples, the photoactive material of a device may contain aphotoactive compound that is an electron acceptor compound describedherein and the electron donor compound comprises a boron-dipyrromethene(BODIPY) compound, a phthalocyanine compound, a naphthalocyaninecompound, a metal dithiolate (MDT) compound, or a dithiophene squarinecompound. Combinations thereof may also be used. Examples of usefulBODIPY compounds include, but are not limited to, those described inU.S. patent application Ser. No. 16/010,371, filed on Jun. 15, 2018,which is hereby incorporated by reference. Examples of usefulphthalocyanine and naphthalocyanine compounds include, but are notlimited to, those described in U.S. patent application Ser. No.16/010,365, filed on Jun. 15, 2018, which is hereby incorporated byreference. Examples of useful MDT compounds include, but are not limitedto, those described in U.S. patent application Ser. No. 16/010,369,filed on Jun. 15, 2018, which is hereby incorporated by reference.Examples of useful dithiophene squarine compounds include, but are notlimited to, those described in U.S. patent application Ser. No.16/010,374, filed on Jun. 15, 2018, which is hereby incorporated byreference. In some examples, a photoactive layer contains a BODIPYcompound, a phthalocyanine compound, a naphthalocyanine compound, a MDTcompound, a dithiophene squarine compound, or a combination thereof.

Aspects of the invention may be further understood by reference to thefollowing non-limiting examples.

EXAMPLE 1—SYNTHESIS OF EXAMPLE PHOTOACTIVE COMPOUNDS, INCLUDING THOSECONTAINING CORE-DISRUPTED AND INDANDIONE GROUPS

FIGS. 8-34 provide overview of various example synthetic schemesproviding synthetic routes for various photoactive compounds, includingcore disrupted compounds and compounds containing indandione groups.

FIG. 8 provides a synthetic scheme for preparation of compound III byway of compound II.

Compound II: Flask 1: To a dry three neck flask4H-Cyclopenta[1,2-b:5,4-b′]di thiophene (10.08 g, 0.0565 mol) and 240 mLof anhydrous THE were added under nitrogen protection. The reactionflask was then cooled to −20° C. and n-BuLi (2.5 M in Hexanes, 22.4 mL,0.056 mol) was added dropwise. Temperature was kept between −25° C. and−18° C. for 30 minutes under agitation with a magnetically coupledspinbar.

Flask 2: To a dry second three neck flask 1,5-dibromopentane was addedto 80 mL of anhydrous THF, placed under nitrogen protection, and thencooled to −70° C. with a dry ice and acetone dewar flask. A dry additionfunnel was added to one of the flask ports and the reaction mixture fromFlask 1 was cannulated into the addition funnel added dropwise over thecourse of 30 minutes to the flask 2 at −70° C. This new reaction mixturewas stirred for 30 minutes at −70° C. and 80 mL of anhydrous THE wasrinsed through the addition funnel to further dilute the reaction. Asecond equivalent of n-BuLi was added dropwise (2.5 M in Hexanes, 22.4mL, 0.056 mol) to this reaction mixture and allowed to stir for 30minutes at −70° C. before gradual warming to room temperature over thecourse of 30 additional minutes. The reaction continued for 1 hour atroom temperature before workup through addition to 600 mL of deionizedwater and 3× extractions of 300 mL of diethyl ether, drying over sodiumsulfate, and concentration in vacuo to yield crude product. Purificationwas achieved via column chromatography on Silica-60 with Heptane toyield compound II (6.13 g, 44% yield).

Compound III: To a dry three neck flask compound II (0.40 g, 0.00162mol) and 40 mL of anhydrous diethyl ether were added under nitrogenprotection. TMEDA was added to the reaction mixture dropwise at roomtemperature, then the flask was cooled to −40° C. n-BuLi (2.5 M inHexanes, 1.30 mL, 0.00325 mol) was added to the reaction mixturedropwise. The reaction mixture was allowed to warm to room temperatureover 30 minutes and then was mixed for an additional 30 minutes at roomtemperature. The flask was then cooled to −40° C. and anhydrous DMF(0.50 mL, 0.00649 mol) was added. The reaction was allowed to mix for 30minutes at −40° C. and was then warmed gradually to mix overnight atroom temperature. Workup was accomplished by pouring the reactionmixture into 100 mL of 20% NH₄Cl (aq) solution, 3× extraction withdichloromethane, and drying over sodium sulfate to yield crude compoundIII. Purification by column chromatography on Silica-60 elutes withDichloromethane-Heptane to yield compound III (0.348 g, 71% yield).

FIG. 9 provides synthetic schemes for preparation of variouscore-disrupted photoactive compounds:

Compound V: To a 3-neck flask equipped with a condenser and magneticstir bar, compound III (0.15 g, 0.0005 mol), compound IV (0.43 g, 0.002mol), and 60 mL of acetic anhydride were added. The flask was purgedwith nitrogen then stirred at room temperature for 30 minutes beforebeing heated to 90° C. and stirred for an additional hour. 200 mL ofwater were added to the cooled reaction and the precipitate was filteredto obtain compound V. This compound was sublimed in 5% yield. λ_(max)(DCM): 696 nm.

Compound VII: To a 3-neck flask equipped with a condenser and magneticstir bar, compound III (1.0 eq) compound VI (4.0 eq), and anhydrouschloroform were added. The flask was purged with nitrogen then pyridine(20.0 eq) was added dropwise. The mixture was stirred at roomtemperature for 30 minutes then heated to reflux and stirred for 48hours under nitrogen. The reaction mixture was cooled to roomtemperature, concentrated in vacuo, then resuspended in hot isopropanol.The suspension was filtered and washed with additional isopropanol thendried to obtain compound VII. This compound was sublimed in 0% yield.λ_(max) (DCM): 682 nm.

Compound IX: To a 3-neck flask equipped with a condenser and magneticstir bar, compound III (1.0 eq) compound VIII (4.0 eq), and anhydrouschloroform were added. The flask was purged with nitrogen then pyridine(20.0 eq) was added dropwise. The mixture was heated to reflux andstirred for 18 hours under nitrogen. The reaction mixture was cooled toroom temperature then poured into 200 mL of cold methanol. Thesuspension was filtered then washed with additional methanol to affordcompound IX as a shiny green solid with limited solubility in 80% yield.This compound was sublimed in 30% yield. λ_(max) (DCM): 609 nm.

Compound XI: Compound XI was synthesized from compound III using thesame method as used for compound IX, substituting compound X in place ofcompound VIII. Compound XI was sublimed in 13% yield. λ_(max) (DCM): 676nm.

FIG. 10 provides synthetic schemes for preparation of variouscore-disrupted photoactive compounds:

Compound XIII: Compound XIII was synthesized from compound III using thesame method as used for compound IX, substituting compound XII in placeof compound VIII. Compound XIII was sublimed in 65-85% yield. λ_(max)(DCM): 593 nm.

Compound XV: Compound XV was synthesized from compound III using thesame method as used for compound IX, substituting compound XIV in placeof compound VIII, in 73% yield. Compound XV was sublimed in 9% yield.λ_(max) (DCM): 611 nm.

Compound XVII: Compound XVII was synthesized from compound III using thesame method as used for compound VII, substituting compound XVI in placeof compound VI, in 99% yield. This compound was sublimed in 75-88%yield. λ_(max) (DCM): 599 nm.

FIG. 11 provides a synthetic scheme for preparation of a core-disruptedphotoactive compound:

Compound XVIII was synthesized from compound I using the same method asused for compound II, substituting 1,5-Pentanediol, 3,3-dimethyl-,1,5-dimethanesulfonate in place of 1,5-dibromopentane, in 55% yield.

Compound XIX was synthesized using the same method as used for compoundIII, substituting compound XVIII in place of compound II, in 51% yield.

Compound XX was synthesized from compound VIII using the same method asused for compound IX, substituting compound XIX in place of compoundIII, in 41% yield. Compound XX was sublimed in 12% yield.

FIG. 12 provides a synthetic scheme for preparation of a core-disruptedphotoactive compound:

Compound XXI was synthesized from compound I using the same method asused for compound II, substituting 1,4-dibromobutane in place of1,5-dibromopentane, in 69% yield.

Compound XXII was synthesized using the same method as used for compoundIII, substituting compound XXI in place of compound II, in 39% yield.

Compound XXIII was synthesized from compound VIII using the same methodas used for compound IX, substituting compound XXII in place of compoundIII. Compound XXIII was sublimed in 12% yield. λ_(max) (DCM): 686 nm.

FIG. 13 provides a synthetic scheme for preparation of a core-disruptedphotoactive compound:

Compound XXIV was synthesized from compound I using the same method asused for compound II, substituting and 1,4-Butanediol,2,3-dimethyldimethanesulfonate in place of 1,5-dibromopentane, in 53%yield.

Compound XXV was synthesized using the same method as used for compoundIII, substituting compound XXIV in place of compound II, in 51% yield.

Compound XXVI was synthesized from compound VIII using the same methodas used for compound IX, substituting compound XXV in place of compoundIII, in 93% yield. Compound XXVI was sublimed in 5% yield. λ_(max)(DCM): 680 nm.

FIG. 14 provides a synthetic scheme for preparation of compound XXVIIIby way of compound XXVII.

Compound XXVII: To a dry three neck flask compound I (9 g, 0.050 mol),potassium hydroxide (9.06 g, 0.162 mol), and 250 mL of anhydrous DMSOwere added under nitrogen atmosphere. The reaction flask was purged withnitrogen and magnetically stirred at room temperature for a period of 45minutes. Bromoethane (11.0 g, 0.101 mol) was added dropwise and themixture was left to stir for 18 hours. The reaction mixture was dilutedwith ethyl acetate then washed with water followed by a saturated sodiumchloride solution. The organic layer was dried over anhydrous MgSO₄ thenfiltered and concentrated in vacuo to yield the crude product as an oil.Purification was achieve via column chromatography on Silica-60 using aheptane/ethyl acetate gradient for elution to yield compound XXVII as anoil (11 g) in 93% yield.

Compound XXVIII was synthesized using the same method as used forcompound III, substituting compound XXVII in place of compound II, in79% yield.

FIG. 15 provides synthetic schemes for preparation of variousphotoactive compounds:

Compound XXIX was synthesized from compound X using the same method asused for compound XI, substituting compound XXVIII in place of compoundIII. λ_(max) (DCM): 477 nm.

Compound XXX was synthesized using the same method as used for compoundV, substituting compound XXVIII in place of compound III and compoundVIII in place of compound IV, in 73% yield. λ_(max) (DCM): 676 nm.

Compound XXXI: To a 3-neck flask equipped with a condenser and magneticstir bar, compound XXVIII (0.5 g, 0.002 mol), compound VI (1.59 g, 0.007mol), and 150 mL of anhydrous chloroform were added. The flask waspurged with nitrogen then pyridine (1.63 g, 0.021 mol) was addeddropwise. The mixture was stirred at room temperature for 30 minutesthen heated to reflux and stirred for 18 hours under nitrogen. Thereaction mixture was cooled to room temperature then poured into coldwater. The biphasic mixture was extracted with dichloromethane. Organiclayers were combined, dried over MgSO₄, filtered, and concentrated invacuo to obtain compound XXXI as a dark solid (1.2 g, 98% yield).λ_(max) (DCM): 614 nm.

Compound XXXII was synthesized using the same method as used forcompound IX, substituting compound XXVIII in place of compound III andcompound XII in place of compound VIII. Compound XXXII was sublimed in30% yield.

FIG. 16 provides a synthetic scheme for preparation of anindandione-containing photoactive compound:

Compound XXXIII was synthesized from compound I using the same method asused for compound XXXVII, substituting 1-chloro-2-methylbutane in placeof 1,5-dibromopentane, in 90% yield.

Compound XXXIV was synthesized using the same method as used forcompound III, substituting compound XXXIII in place of compound II, in84% yield.

Compound XXXV: A solution of compound XXXIV (6.37 g, 17.0 mmol, 1 eq)and XVI (12.38 g, 68.0 mmol, 4 eq) in chloroform (640 mL, 100 vol) wassparged with nitrogen for 5 minutes. Pyridine (20.6 mL, 20.2 g, 255mmol, 15 eq) was added slowly over 2 minutes. The solution was thenheated at 60° C. (reflux) for 30 hours. The suspension was cooled to 23°C. and filtered through a pad of Celite (18 g), which was rinsed withdichloromethane (3×100 mL). The combined filtrate was concentrated todryness under reduced pressure to give a crude dark solid (18 g). Thesolid was suspended in dichloromethane (450 mL) at 40° C. (reflux) for 1hour and filtered through a pad of Celite (18 g) rinsing withdichloromethane (2×100 mL). The filtrate was concentrated under reducedpressure to a volume of 200 mL. The solution was heated at 40° C. andtreated with hexanes (360 mL) slowly over 1.5 hours. The suspension wascooled to 23° C. over 2 hours and the solid was collected by vacuumfiltration and washed with a 2 to 1 mixture of hexanes anddichloromethane (3×50 mL). The filtrate was concentrated onto Celite (26g) and purified on an automated Biotage system (Sorbtech 330 g column),eluting with a gradient of 50 to 100% dichloromethane/heptanes) to givecompound XXXV (5.3 g) in 44% yield. This compound was sublimed in 60-80%yield.

FIG. 17 provides a synthetic scheme for preparation of a core-disrupted,indandione-containing photoactive compound:

Compound XXXVI: Compound II (2.5 g, 1.0 eq) was dissolved in 67 mL ofchloroform followed by addition of NBS (3.97 g, 2.2 eq) and the mixturewas stirred in the dark for 12 hours. Upon completion, the reactionmixture was poured into water and the biphasic mixture was extractedwith chloroform. Organic layers were combined, dried over MgSO₄,filtered, and concentrated. The crude material was dry loaded ontosilica gel and purified by CombiFlash. Desired product was eluted withheptane to afford compound XXXVI as an orange solid (3.68 g, 89% yield).

Compound XXXVII: In an oven dried 3-neck RB flask equipped with nitrogeninlet diisopropylamine (2.65 g, 4.0 eq) was dissolved in dry THE (30 mL)and the reaction temp was adjusted to −78° C. followed by dropwiseaddition of n-butyl lithium (2.5 M, 9.8 mL, 4.0 eq) and the reaction wasstirred at 0° C. for 30 mins to generate LDA. In another oven dried 100mL 3-neck RB flask compound XXXVI was dissolved in dry THE (15 mL) andthe reaction temp is adjusted to −78° C. followed by dropwise additionof LDA generated in other RB flask. The mixture was stirred for 30 minat this temperature, and then warmed to room temperature for 2 h. Afterthe mixture was cooled to 0° C., anhydrous DMF (1.2 mL) was added, andthe reaction stirred at this temperature for 30 min. Then the mixturewas allowed to warm to room temperature for 1 h and water (30 mL) wasadded. The organics were extracted (3×30 mL DCM), dried by sodiumsulfate, filtered and concentrated under reduced pressure. The residuewas purified by silica gel chromatography using 24 g column eluted withDCM/Heptane to afford compound XXXVII as yellow solid (1.1 g, 47%yield).

Compound XXXVIII: In an oven dried 100 mL 3-neck RB flask equipped withnitrogen gas inlet, ethyl thioglycolate (0.9 g, 2.0 eq) was addeddropwise to a mixture of compound XXXVII (1.4 g, 1.0 eq) and potassiumcarbonate (1.5 g, 3.0 eq) in DMF (10 mL) at 50° C. under argon. Afteraddition, the mixture was stirred at this temperature for 24 h. TLC(DCM) showed completion of reaction. The reaction was quenched by addingwater (50 mL). Yellow colored precipitate was filtered and purified bysilica gel column eluted with Heptane/DCM. Appropriate fractions werecombined, concentrated, and dried under high vacuum to get compoundXXXVIII (1.05 g, 72% yield).

Compound XXXIX: Lithium aluminum hydride (0.30 g, 3.5 eq)) was suspendedin 15 mL of THE and cooled to 0° C. followed by dropwise addition ofcompound XXXVIII (1.05 g, 1.0 eq)) dissolved in 30 mL THF. An additional10 mL of THF was used to rinse and transfer residue from vials. Thereaction was left to warm to room temperature and stirred overnight. Thereaction was cooled to 0° C. and quenched by slow addition of water.Biphasic mixture was extracted with ether. Organic layers were combined,washed with brine, dried over MgSO₄, filtered and concentrated to yielda brown solid/foam. The crude material was purified by columnchromatography and eluted with Heptanes:EtOAc to afford compound XXXIXas a light yellow solid (0.762 g, 94% yield).

Compound XL: Compound XXXIX (610 mg, 1.0 eq) was added to a dry 3-neck100 mL flask followed by 50 mL of anhydrous DCM. DMP (Dess-Martinperiodinane) (1.9 g, 2.6 eq)) was added portion-wise and the reactionwas stirred under nitrogen overnight. The reaction mixture was dilutedwith ether and washed with 1 N NaOH followed by 1 M Na₂S₂O₃, saturatedbicarb, and finally brine. The organic layer was dried over MgSO₄,filtered, and concentrated. The crude material was dry loaded ontosilica gel and purified by column chromatography. Desired product waseluted with Heptane/EtOAc to afford Compound XL as a yellowish brownsolid (343 mg, 57% yield).

Compound XLI: Compound XL (200 mg, 1.0 eq) was added to a 100 mL 3-neckflask followed by compound XVI (280 mg, 4.0 eq) and 40 mL of DCE. Themixture was purged with nitrogen at room temperature for 20 min thenpyridine (0.85 mL, 12.0 eq) was added dropwise. The reaction was stirredat room temperature for an additional 20 min then heated to reflux andleft to stir for 96 hours. The precipitate was filtered and washed withhot methanol to get compound XLI (120 mg. 49%). This compound wassublimed in 9% yield. λ_(max) (DCM): 610 nm.

FIG. 18 provides a synthetic scheme for preparation of a core-disrupted,indandione-containing photoactive compound including thiophene pimoieties:

Compound XLII: In an oven dried 250 mL 3-neck RB flask, compound II (1.5g, 1.0 eq) was dissolved in dry THE (70 mL) under nitrogen and thereaction temperature was adjusted to −78° C. followed by dropwiseaddition of n-butyl lithium (2.5 M, 5.1 mL, 2.1 eq). The reactionmixture was then stirred at −10 to 0° C. for 1 hr and then re-adjustedto −78° C. followed by dropwise addition of trimethyl tin (1 M solution,18.3 mL, 3.0 eq). The reaction mixture was then stirred at RT. After 18hrs the reaction was quenched by adding water. Organic layer wasseparated, and the aqueous layer was washed with ether (2×50 mL).Combined organic layers were dried over sodium sulfate and concentratedunder vacuum to obtain compound XLII, which used as it is for next step.

Compound XLIII: In a 250 mL 3-neck RB flask equipped with nitrogen lineand condenser, compound XLII (3.5 g, 1.0 eq) and compound5-bromo-thiophene-2-carbaldeyde (2.34 g, 2.0 eq) were dissolved in drytoluene (200 mL) under nitrogen and the solution was purged withnitrogen for 30 mins followed by addition of Pd(PPh₃)₄ (0.7 g, 0.10 eq).The mixture was purged with nitrogen and refluxed for 18 hrs. TLC showedformation of two lower Rf yellow/red colored spots. The reaction mixturewas concentrated under vacuum and purified by autoflash chromatographyusing 80 g silica gel column with DCM/EtOAc to obtain compound XLIII(1.7 g, 60% yield).

Compound XLIV: In an oven dried 500 mL 3-neck RB flask equipped withcondenser and nitrogen inlet compound XLIII (0.5 g, 1.0 eq), compoundXVII (1.0 g, 5.0 eq) and ammonium acetate (1.65 g, 20.0 eq) drydichloroethane (200 mL) under nitrogen and the reaction mixture wasrefluxed at 83° C. for 3 weeks. The reaction mixture was cooled to RTand the dark green color solid was filtered. The solid obtained waswashed with hot methanol and dried under high vacuum to get compoundXLIV (0.85 g, 100% yield). This compound was sublimed in 12-17% yield.λ_(max) (DCM): 654 nm.

FIG. 19 provides a synthetic scheme for preparation of a core-disrupted,indandione-containing photoactive compound:

Compound XLV was synthesized from compound XLII using the same method asused for compound XLIII, substituting5-bromo-4-butyl-thiophene-2-carbaldehyde in place of5-bromo-thiophene-2-carbaldeyde, in 19% yield.

Compound XLVI was synthesized from compound XVI using the same method asused for compound XVII, substituting compound XLV in place of compoundIII, in 100% yield. This compound was sublimed in 3% yield. λ_(max)(DCM): 640 nm.

FIG. 20 provides synthetic schemes for preparation of core-disruptedphotoactive

Compound XLVIII: Compound XLII (1.0 eq), XLVII (2.1 eq) and Pd(PPh₃)₄(0.1 eq) were added to try toluene under nitrogen and the mixture waspurged with nitrogen gas. The reaction mixture was then stirred at 110°C. for 24 hours. The solvent was distilled off under reduced vacuum andthe residue was purified by silica gel column chromatography usingdichloromethane to obtained compound XLVIII.

Compound L was synthesized from compound XLII using the same method asused for compound XLVIII, substituting compound XLIX in place ofcompound XLVII.

FIG. 21 provides a synthetic scheme for preparation of compound LII byway of compound LI.

Compound LI: A suspension of 3,3′-dibromo-2,2′-bithiophene (15 g, 1.0eq), sodium tert-butoxide (10 g, 2.2 eq), Pd₂(dba)₃ (1.26 g, 0.03 eq)and BINAP (3.45 g, 0.12 eq) in anhydrous toluene was purged withnitrogen for 30 minutes followed by addition of 2-methylbutylamine (4.05g, 1.0 eq) and the reaction mixture was refluxed at 110° C. for 48 hoursunder nitrogen atmosphere. The reaction mixture was then poured in waterand extracted with dichloromethane (200 mL). The organic layer wasseparated, dried over sodium sulfate, and concentrated under vacuum. Thecrude material was purified by flash chromatography to obtain compoundLI (9.6 g, 76% yield).

Compound LII: To a dry three neck flask Compound LI (4.3 g, 1.0 eq) andwas dissolved in anhydrous THE under nitrogen atmosphere followed byaddition of TMEDA (5.21 g, 2.6 eq). n-Butyl lithium (2.5 M, 18 mL, 2.6eq) was then added dropwise and the reaction mix continued to stir at−40° C. for 30 min and then warmed to room temperature and the mixturewas stirred at room temperature for 2 hr. The reaction mixture wascooled back to −40° C. followed by addition dry DMF (3.27 g, 2.6 eq)dropwise and stirred at room temperature overnight. Workup wasaccomplished by pouring the reaction mixture into 20% NH₄Cl (aq)solution, 3× extraction with dichloromethane, and drying over sodiumsulfate to yield crude product. Purification was done by columnchromatography on silica gel with Dichloromethane-Heptane to yieldcompound LII (2.5 g, 62% yield).

FIG. 22 provides synthetic schemes for preparation of variousphotoactive compounds:

Compound LIII: Compound LII (1.0 eq) and X (4.0 eq) were mixed withanhydrous chloroform under nitrogen atmosphere followed by addition ofpyridine (20 eq). The reaction mixture was refluxed for 48 hours andthen cooled to room temperature. The precipitate was flirted and washedwith hot isopropyl alcohol to afford compound IV (60% yield).

Compound LIV was synthesized from compound LII using the same method asused for compound LIII, substituting compound VIII in place of compoundX, in 90% yield.

Compound LVI was synthesized using compound LII and LV using a similarmethod as used for compound LIII, substituting compound LV in place ofcompound X, in 75% yield.

FIG. 23 provides a synthetic scheme for preparation of a photoactivecompound:

Compound LVIII: A suspension of compound LVII (1 eq), potassiumhydroxide (7.5 eq) and potassium iodide (0.04 eq) in anhydrous dimethylsulfoxide (25 vol) was sparged with nitrogen for 5 min.1-Chloro-2-methylbutane (4.6 eq) was added slowly over 10 min undernitrogen. The resulting dark suspension was stirred at 21° C. for 18 hr.The reaction mixture was cooled to 10° C. Water (25 vol) was addeddropwise over 5 min (T_(max)=14° C.). The mixture was then dilutedfurther with water (25 vol) and extracted into heptane (60 vol, then2×30 vol). The organics were combined and washed with water (25 vol),dried (Na₂SO₄) and filtered. The filtrates were concentrated in vacuo togive the crude product as a dark brown oil. Purification by flash columnchromatography (SiO₂) eluting with heptane gave compound LVIII as ayellow oil that solidified on standing (67% yield).

Compound LIX: Phosphorus oxychloride (20 eq) was added dropwise over 20min to an oven dried flask containing a solution of DMF (20 eq) in DCE(15 vol) under an atmosphere of nitrogen. The resulting yellow solutionwas stirred at ambient temperature for 3 hr. A solution of compoundLVIII (1 eq) in dichloroethane (37.5 vol) was then added dropwise over15 min (no exotherm observed). The solution was then heated to at 60° C.for 42 hr and then cooled to room temperature. The solvent was removedon the rotary evaporator. The resulting brown gum was quenched withice-water (25 vol), then basified to ca. pH 8 with sat. sodiumbicarbonate solution. The resulting suspension was then stirred at roomtemperature for 2 hr before extracting into DCM (50 vol, then 2×25 vol).The organics were dried (Na₂SO₄) and concentrated in vacuo to give thecompound LIX as brown solid (72%).

Compound LX: A solution of compound LIX (1 eq) and XVI (4 eq) inchloroform (56 vol) was sparged with nitrogen for 5 min. Pyridine (15eq) was then added causing a rise in temperature of 15.5° C. to 17.5° C.The mixture was then heated at reflux. After 48 hr, the dark purplereaction solution was cooled to room temperature. A small sample wasremoved, concentrated, and analysed by 1H NMR spectroscopy to show thatall aldehydes had been consumed. The reaction mixture was concentratedon the rotary evaporator to provide crude product as a dark purplesolid, which was further purified by hot methanol wash to get compoundLX (90%). This compound was sublimed in 65% yield.

Compound LXI and compound LXII were synthesized using the same methodsas compound LX, but different reagents were used in place of1-chloro-2-methylbutane (e.g., chloromethane or p-chlorotoluene) and inplace of compound XVI (e.g., compound X):

FIG. 24 provides a synthetic scheme for preparation of compound LXIV byway of compound LXIII.

Compound LXIII: n-Butyl lithium (2.0 eq) was added to dry THE in a2-neck RB flask and the reaction mixture was cooled to −78° C. followedby dropwise addition of 3,3′-dibromo-2,2′-bithiophene (1.0 eq) dissolvedin THE and the reaction mixture was stirred for 1 hour. A solution ofdichlorosilane (1.1 eq) in THE was added to the reaction mixture keepingreaction temperature below −70° C. After addition, the reaction mixturewas stirred at room temperature overnight. The reaction was thenquenched by adding aqueous ammonium chloride and the product wasextracted with ether and purified by column chromatography usingheptane. The product obtained after chromatography was further purifiedby vacuum distillation at 390° C. to obtain compound LXIII in 12% yield.

Compound LXIV: Phosphorus oxychloride (10 eq) was added dropwise over 20min to an oven dried flask containing a solution of DMF (20 eq) in DCE)under an atmosphere of nitrogen at 0° C. The resulting yellow solutionwas stirred at ambient temperature for 3 hr. A solution of compoundLXIII (1 eq) in dichloroethane was then added dropwise over 15 min. Thesolution was then heated to 90° C. After 4 hours, the reaction mixturewas cooled to room temperature and poured into saturated sodium acetatesolution under ice bath. The product was extracted with dichloromethane.Organic layer was dried with sodium sulphate, concentrated under vacuumand purified by column chromatography to obtain compound LXIV in 60%yield.

FIG. 25 provides synthetic schemes for preparation of variouscore-disrupted photoactive compounds:

Compound LXV: Compound LXIV (1.0 eq) and X (4.0 eq) were refluxed withpyridine (15.0 eq) and chloroform for 48 hours. The reaction mixture wasfiltered while hot and the precipitate was washed with chloroform toobtained compound LXV in 82% yield. This compound was sublimed in 7%yield.

Compound LXVI was synthesized from compound LXIV using a similar methodas used for compound LXV, substituting compound VIII in place ofcompound X. Compound LXVI was sublimed in 10% yield.

Compound LXVII: Compound LXIV (1.0 eq) and LV (4.0 eq) were mixed withacetic anhydride and the mixture was degassed with nitrogen. Thereaction mixture was then stirred for 15 min at 50° C. followed by 4hours at 80° C. The reaction mixture was then cooled to room temperatureand filtered. The precipitate was washed with heptane and trituratedwith dichloromethane/methanol (8/2) to obtain compound LXVII (82%). Thiscompound was sublimed in 11% yield.

Compound LXVIII was synthesized from compound LV using the same methodas used for LXVII, substituting compound III in place of compound LXIV.Compound LXVIII was sublimed in 31% yield:

FIG. 26 provides a synthetic scheme for preparation of a photoactivecompound:

Compound LXIX: To a 3 neck-flaskBenzo[1,2-b:4,5-b′]dithiophene-4,8-dione, zinc, sodium hydroxide, and126 mL of water were added. The mixture was refluxed for 3 hours thencooled to room temperature. Bromoethane (4.45 g, 0.041 mol) andtetrabutylammonium bromide (0.44 g, 0.001 mol) were added and thereaction was refluxed for an additional 6 hours. The reaction was cooledto room temperature, diluted with water, and extracted with ethylacetate. The organic layers were combined, dried over MgSO₄, filtered,and concentrated in vacuo to afford the crude product as an oil.Purification was achieved via column chromatography on Silica-60 with aheptane/dichloromethane gradient for elution to yield compound LXIX(2.37 g, 63% yield).

Compound LXX was synthesized using the same method as used for compoundIII, substituting compound LXIX in place of compound II, in 20% yield.

Compound LXXI was synthesized from compound VIII using the same methodas used for compound IX, substituting compound LXX in place of compoundIII, in 80% yield. Compound LXIXI was sublimed in 0% yield. λ_(max)(DCM): 494 nm.

FIGS. 27-34 provide overviews of various example synthetic schemesproviding synthetic routes for various photoactive compounds, includingcompounds containing indandione groups. FIG. 27 provides a syntheticscheme for preparation of an indandione containing photoactive compound:

Compound LXXIII: In an oven dried 2 L 3-neck flask equipped withnitrogen inlet and condenser, a solution of compound LXXII (30.0 g,0.053 mol), sodium tert-butoxide (51.12 g, 0.005 mol), Pd(dba)₂ (3.06 g,0.005 mol), and dppf (11.80 g, 0.021 mol) in 900 mL of dry toluene wasstirred for 20 min at room temperature under nitrogen atmosphere. Afteraddition of 2-methylbutylamine (13.91 g, 0.532 mol), the mixture wasstirred at 110° C. for 20 h. The reaction was cooled to room temperaturethen diluted with water. The biphasic mixture was extracted with DCM.Organic layers were combined, dried over sodium sulphate, filtered, andconcentrated in vacuo. The crude product was purified by autoflashchromatography using 330 g+125 g (stacked) silica gel columns elutedwith Heptane/DCM to afford product as a white foam (10.3 g, 47% yield).

Compound LXXIV: A mixture of DMF (31 g, 0.4 mol) and POCl₃ (65 g, 0.4mol) in 250 mL of dichloroethane was stirred for 2 h at roomtemperature. Compound LXXIII (7.0 g, 0.017 mol) dissolved in 1.2 L ofDCE was added and the mixture was stirred at 60° C. for 4 d. TLC andLC-MS after mini work-up showed completion of reaction. The reactionmixture was concentrated under vacuum and residue wasneutralized/hydrolyzed with satd. sod. Bicarb. until the pH is neutral.The red precipitate was filtered and washed with water. The wet crudematerial was stirred with DCM (700 mL) and dried with sod. sulfate. DCMsolution was concentrated and slurried over silica gel (˜40 g) andpurified by autoflash chromatography using 330 g column eluted withDCM/EtOAc (0-20%). Appropriate fractions were combined and concentratedto get compound III (7.2 g, 90%) as orange solid.

Compound LXXV: In an oven dried 250 mL 3-neck flask equipped withcondenser and nitrogen inlet compound LXXIV (1.5 g, 0.003 mol), compoundXVI (2.9 g, 0.016 mol), and ammonium acetate (3.68 g, 0.048 mol) weredissolved in 800 mL dichloroethane under argon atmosphere. The solutionwas refluxed for 72 h. The reaction mixture was filtered hot and thegreen precipitate was washed with hot methanol to afford the desiredproduct (200 mg, 42% yield). This compound was sublimed in 38% yield.λ_(max) (DCM): 658 nm.

FIG. 28 provides a synthetic scheme for preparation of an indandionecontaining photoactive compound:

Compound LXXVI: A mixture of compound LXXII (6.0 g, 10.6 mmol, 1.0 eq),sodium tert-butoxide (12.3 g, 127 mmol, 12 eq), Pd(dba)₂ (735 mg, 1.27mmol, 0.12 eq), and dppf (2.95 g, 5.32 mmol, 0.5 eq) in toluene (220 mL)was sparged with argon for 30 minutes at room temperature.2-Ethylhexylamine (7.0 mL, 42.6 mmol, 4 eq) was added and the mixturewas heated at 110° C. for 20 hours. After cooling to room temperature,the reaction was diluted with water (100 mL). The aqueous layer wasseparated and extracted with dichloromethane (2×100 mL). The combinedorganic layers were dried over anhydrous sodium sulfate and concentratedunder reduced pressure. The crude material was absorbed onto celite (60g) and purified on a Buchi automated chromatography system (Sorbtechsilica gel column, 330 g), eluting with a gradient of 0 to 30%dichloromethane in hexanes to give the product as a light yellow solid(2.1 g, 40% yield).

Compound LXXVII: Compound LXXVII was prepared as described in thesynthesis of compound LXXIV, substituting compound LXXVI in place ofcompound LXXIII. The product was obtained in 86% yield.

Compound LXXVIII: Compound LXXVIII was prepared as described in thesynthesis of compound LXXV, substituting compound LXXVII in place ofcompound LXXIV. The product was obtained in 74% yield. This compound wassublimed in 10% yield. λ_(max) (DCM): 658 nm

FIG. 29 provides a synthetic scheme for preparation of an indandionecontaining photoactive compound:

Compound LXXIX: A suspension of compound LXXII (15.55 g, 27.57 mmol, 1eq), bis(dibenzylideneacetone)palladium (1.59 g, 2.76 mmol, 0.1 eq),1,1′-bis(diphenylphosphino)ferrocene (6.11 g, 11.0 mmol, 0.4 eq) andsodium tert-butoxide (42.4 g, 441 mmol, 16 eq) in toluene (180 mL, 12vol) was sparged with a stream of nitrogen for 10 minutes. Thesuspension was then stirred under nitrogen at 23° C. for 20 minutes.Isopentylamine (6.25 g, 8.32 mL, 71.68 mmol, 2.6 eq) was then addedunder nitrogen. The resulting suspension was heated at 104° C. for 16hours. The suspension was cooled to 23° C. and treated slowly with icewater (100 mL). The biphasic mixture was filtered through a pad ofCelite (20 g) and the layers were separated. The organic layer wasconcentrated under reduced pressure. The Celite pad was rinsed withdichloromethane (3×100 mL). The dichloromethane filtrate was combinedwith the above crude product and concentrated onto Celite (22 g). Thesolid was purified on an Interchim automated chromatography system (330g Sorbtech), eluting with a gradient of 10 to 20% dichloromethane inheptanes to give a yellow solid (4.9 g). This material was trituratedwith methanol (20 mL) at 23° C. for 2 hours and the solid was collectedby vacuum filtration, rinsed with methanol (2×5 mL) and dried undervacuum at 23° C. for 15 hours to afford the product as a light yellowsolid (4.86 g, 42% yield).

Compound LXXX: Compound LXXX was prepared as described in the synthesisof compound LXXIV, substituting compound LXXIX in place of compoundLXXIII (3.97 g, 75% yield).

Compound LXXXI: Compound LXXX (1.50 g, 3.19 mmol) was dissolved indichloroethane (175 mL) at 75° C. Sodium sulfate (5 g) was added. Thesuspension was kept at 75° C. for 20 minutes and hot filtered into a 1-L3-neck round-bottom flask rinsing with hot dichloroethane (75° C., 3×100mL). 5,6-Difluoro-1H-indene-1,3(2H)-dione (2.90 g, 15.9 mmol, 5 eq),ammonium acetate (3.69 g, 47.85 mmol, 15 eq) and additionaldichloroethane (275 mL) were added to the reaction. The solution wasthen heated at 81° C. (reflux) for 68 hours. Additional5,6-difluoro-1H-indene-1,3(2H)-dione (1.16 g, 6.38 mmol, 2 eq) andammonium acetate (1.48 g, 19.1 mmol, 6 eq) were added. The suspensionwas heated at 81° C. (reflux) for 42 hours. The suspension was cooled to23° C. over 2 hours and the solid was collected via vacuum filtrationand rinsed with hot methanol (60° C., 3×30 mL). The solid (3.97 g) wastriturated with chloroform (400 mL) at 23° C. for 20 hours. The solidwas collected by vacuum filtration, rinsed with chloroform (3×20 mL) andfurther dried under vacuum oven at 50° C. for 5 hours to produce theproduct as a dark green solid in quantitative yield. This compound wassublimed in 23% yield.

FIG. 30 provides a synthetic scheme for preparation of an indandionecontaining photoactive compound:

Compound LXXXII: 2.5 M n-Butyl lithium in hexanes (3.1 mL, 7.82 mmol, 3eq) was added dropwise over 15 minutes to a solution of compound LXXVI(1.3 g, 2.61 mmol, 1.0 eq) in anhydrous THE (60 mL) at −78° C. Afterstirring for 2 hours, 1 M trimethyl tin chloride in THE (10.5 mL, 10.5mmol, 4 eq) was added dropwise over 15 minutes. After stirring for 30minutes, the reaction was slowly warmed to room temperature and stirredovernight. The reaction was quenched with ice water (20 mL) andextracted with ether (3×50 mL). The combined organic layers were driedover sodium sulfate and concentrated under reduced pressure. The residuewas dried under vacuum at 25° C. for 5 hours to give compound XII as alight brown oil (2.1 g, quantitative yield).

Compound LXXXIV: A mixture of compound LXXXII (1.3 g, 1.58 mmol, 1.0eq), compound LXXXIII (1.6 g, 4.74 mmol, 3 eq),tetra-kistriphenylphosphine palladium (185 mg, 0.16 mmol, 0.1 eq), andcopper (I) iodide (30 mg, 0.16 mmol, 0.1 eq) in toluene (16 mL) wassparged with argon for 15 minutes at room temperature. After heating at110° C. overnight, the reaction was cooled to room temperature andconcentrated under reduced pressure. The crude material was absorbedonto celite (40 g) and purified on a Buchi automated chromatographysystem (Sorbtech silica gel column, 120 g), eluting with a gradient of20 to 100% dichloromethane in hexanes. The pure fractions were combined,concentrated and resultant solid was dried under vacuum at 50° C.overnight to give compound LXXXIV as a brown solid (970 mg, 60% yield).This compound was sublimed in 0% yield. λ_(max) (DCM): 707 nm.

FIG. 31 provides a synthetic scheme for preparation of an indandionecontaining photoactive compound:

Compound LXXXV: A solution of compound LXXII (10 g, 17.73 mmol, 1.0 eq),cyclohexylmethylamine (4.41 g, 39.00 mmol, 2.2 eq), sodium tert-butoxide(10.22 g, 10.64 mmol, 6.0 eq) and 1,1′-bis(diphenylphosphino)ferrocene(0.20 g, 0.36 mmol, 0.02 eq) in anhydrous toluene (80.0 mL) was spargedwith nitrogen for 20 minutes Bis(diphenylphosphino)ferrocene palladiumdichloride-dichloromethane adduct (2.90 g, 3.55 mmol, 0.2 eq) was addedand the mixture was stirred at 90° C. for 17 hours. After cooling toroom temperature, the mixture was concentrated under reduced pressure,diluted with saturated ammonium chloride (100 mL), and extracted withdichloromethane (2×500 mL). The combined organic layers were washed withsaturated brine (200 mL) and concentrated under reduced pressure afteradding Celite (100 g). The resultant Celite mixture was purified on aBiotage automated chromatography system (Sorbtech 330 g, 60 μm silicagel column), eluting with a gradient of 0 to 30% dichloromethane inhexanes. The product fractions were combined, concentrated, andchromatographed again using a Biotage automated chromatography system(Sorbtech 330 g, 60 μm silica gel column) eluting with a gradient of 10to 20% dichloromethane in hexanes. The product was dried under vacuum at50° C. overnight to give compound XV as a beige solid (2.73 g, 33%yield). Further trituration of the crude material with methanol providedpure product as a beige solid (1.502 g, 87% recovery yield).

Compound LXXXVI: Compound LXXXVI was synthesized using the same methodas described for preparing compound LXXIV, substituting compound LXXXVin place of compound LXXIII. Product was obtained in 91% yield.

Compound LXXXVII: Compound LXXII was synthesized using the same methodas described for preparing compound LXXV, substituting compound LXXXVIin place of compound LXXIV. This compound was sublimed in 14% yield.

FIG. 32 provides a synthetic scheme for preparation of an indandionecontaining photoactive compound:

Compound LXXXVIII: A solution of compound LXXII (8.6 g, 15.2 mmol, 1 eq)and pentan-2-amine (5 mL, 45.5 mmol, 3 eq) in toluene (200 mL) wassparged with nitrogen for 15 minutes. Concurrently, in another flask, amixture of Pd(dba)₂ (0.9 g, 1.5 mmol, 0.1 eq) and dppf (3.4 g, 6.1 mmol,0.4 eq) in toluene (100 mL) was sparged with nitrogen for 15 minutes andtransferred via a canula to the first mixture. Sodium tert-butoxide(14.5 g, 152 mmol, 10 eq) was added to the mixture. After refluxing for20 hours, the reaction mixture was cooled to room temperature andconcentrated under reduced pressure. The residue was dissolved indichloromethane (300 mL) and washed with water (250 mL). The aqueouslayer was extracted with dichloromethane (2×150 mL). The combinedorganic layers were dried over sodium sulfate, filtered, andconcentrated under reduced pressure. The residue was absorbed ontoCelite (120 g) and purified on an Interchim automated chromatographysystem (Sorbtech 220 g silica column), eluting with a gradient of 0 to20% dichloromethane in hexanes to give the product as a yellow solid(1.6 g, 26% yield).

Compound LXXXIX: Compound LXXXIX was synthesized using the same methodas described for preparing compound LXXIV, substituting compoundLXXXVIII in place of compound LXXIII. Product was obtained in 95% yield.

Compound XC: Compound XC was synthesized using the same method asdescribed for preparing compound LXXV, substituting compound LXXXIX inplace of compound LXXIV. Product was obtained in 47% yield. Thiscompound was sublimed in 48% yield. λ_(max) (DCM): 659 nm.

FIG. 33 provides a synthetic scheme for preparation of an indandionecontaining photoactive compound:

Compound XCI: In an oven dried 2 L 3-neck flask equipped with nitrogeninlet and condenser, a solution of compound LXII (3.0 g, 0.005 mol),sodium tert-butoxide (5.11 g, 0.053 mol), and Pd(dba)₂ (0.31 g, 0.001mol), and dppf (1.18 g, 0.002 mol) in 90 mL of dry toluene was stirredfor 20 min at room temperature under nitrogen atmosphere. After additionof 4,4,4-trifluoro-2-methylbutan-1-amine hydrochloride (2.83 g, 0.016mol), the mixture was stirred at 110° C. for 20 h. The reaction wascooled to room temperature then diluted with water. The biphasic mixturewas extracted with DCM (100 mL). Organic layers were combined, driedover sodium sulfate, and concentrated in vacuo. The crude product waspurified by autoflash chromatography using 80 g silica gel column elutedwith Heptane/DCM. Product was obtained as yellow solid (1.08 g, 39%yield).

Compound XCII: Compound XCII was synthesized using the same method asdescribed for preparing compound LXXIV, substituting compound XCI inplace of compound LXXIII. Product was obtained in 88% yield.

Compound XCIII: Compound XCIII was synthesized using the same method asdescribed for preparing compound LXXV, substituting compound XCII inplace of compound LXXIV. Product was obtained in quantitative yield.This compound was sublimed in 52% yield. λ_(max) (DCM): 644 nm.

FIG. 34 provides synthetic schemes for preparation of indandionecontaining photoactive compounds:

Compound XCIV: In an oven dried 1 L 3-neck flask equipped with condenserand nitrogen inlet compound LXXIV (2.05 g, 0.004 mol), compound XII(3.18 g, 0.022 mol), and ammonium acetate (5.04 g, 0.065 mol) weredissolved in 500 mL dichloroethane under nitrogen atmosphere. Thesolution was refluxed for about 48 hours then cooled to roomtemperature. The green precipitate was filtered off and washed with hotmethanol to afford the desired product (1.6 g, 50% yield). The filtratewas concentrated under vacuum and the residue was washed with a hotmixture of methanol (100 mL) and DCE (50 mL). The green solid obtainedwas dried under high vacuum at 60° C. overnight to obtain additionalproduct with (1.75 g, 55% yield). This compound was sublimed in 40%yield. λ_(max) (DCM): 646 nm.

Compound XCVI: In an oven dried 2 L 3-neck flask equipped with condenserand nitrogen inlet compound LXXIV (1.0 g, 0.002 mol), compound XCV (2.27g, 0.011 mol), and ammonium acetate (4.09 g, 0.053 mol) were dissolvedin 700 mL dichloroethane under argon atmosphere. The solution wasrefluxed for 2 days then cooled to room temperature and concentratedunder vacuum to ¼ of its volume and diluted by methanol (300 mL). Theresulting precipitate was filtered off and washed with hot methanol toafford desired product as a green solid (1.33 g, 72.7% yield). Thiscompound was sublimed in 26% yield. λ_(max) (DCM): 668 nm.

EXAMPLE 2—SYNTHESIS OF EXAMPLE CORE DISRUPTED PHOTOACTIVE COMPOUNDSCONTAINING IMINE LINKED INDANDIONE GROUPS

FIG. 35 provides an overview of an example synthetic scheme providing asynthetic route for a core disrupted photoactive compound containingimine linked indandione groups:

Synthesis of the compounds depicted in FIG. 35 was performed as follows:

Compound XCVIII: To a 40 mL scintillation vial attached to an adaptorwith a reflux condenser in a heating block Ninhydrin (compound XCVII,1.44 g, 0.00808 mol), Hydroxylamine HCl (0.60 g, 0.00863 mol), deionizedwater (14 mL), and a magnetic spinbar were added. The reaction mixturewas heated quickly to 100° C. and allowed to reflux for 15 minutes underatmosphere. As the reaction progressed, the solids were dissolved and ayellow precipitate began to form. Workup was accomplished by cooling toroom temperature, filtering, and washing with cold water to collectcompound XCVIII in 90% yield (1.28 g).

Compound XCIX: To a 40 mL scintillation vial with a magnetically coupledspinbar in a heating block compound XCVIII (1.0 g, 0.0571 mol) andacetic anhydride (1.5 mL) were added. The mixture was heated to reflux,˜140° C. and the mixture began to completely melt together and mix at70° C. The reaction was refluxed for 25 minutes and then rapidly cooledto room temperature. An ice bath was used to precipitate the productinside the vial, which was then washed with diethyl ether (10 mL, 4×)and petroleum ether to produce compound XCIX in in 93.0% yield (1.1532g).

Compound C: To a dry three neck flask with an internal thermocouple anda magnetically coupled spinbar compound XLII (0.158 g, 0.000276 mol),compound XCIX (0.1 g, 0.00046 mol) CuTC (0.035 g, 0.000184 mol), andanhydrous THE (15 mL) were added under nitrogen protection. Mixture wassonicated to help dissolve CuTC and then mixed at room temperature for16 hours. Solution was concentrated in vacuo and then washed with hotisopropyl alcohol 3× and then cold dichloromethane 2× to obtain compoundC in 21.1% yield.

EXAMPLE 3—OPTICAL PROPERTIES OF IMINE-LINKED PHOTOACTIVE COMPOUNDS

Compounds XIII and C were synthesized according to the schemes describedherein in Examples 1 and 2 to evaluate the difference in opticalproperties between a photoactive compound with an alkene linker and ananalog core disrupted photoactive compound with an imine linker:

The compounds were dissolved into a solution at ˜1 micromolarconcentration and their ultraviolet-visible (UV-vis) absorption spectrumwas obtained. FIG. 36 provides the normalized UV-vis absorbance profile,showing a peak absorbance by the alkene linked compound at about 590 nmand a peak absorbance by the imine linked compound at about 670 nm.

EXAMPLE 4—SUBLIMATION OF PHOTOACTIVE COMPOUNDS CONTAINING COREDISRUPTION AND INDANDIONES

Several photoactive compounds were synthesized according to the schemesdescribed above in Example 1 to evaluate the difference in sublimationproperties between photoactive compounds containing core disrupted donormoieties and non-disrupted donor moieties as well as the difference insublimation properties between photoactive compounds containingindandione-based acceptor moieties and photoactive compounds containingdicyanomethyleneindanone-based acceptor moieties. The following coredisrupted dicyanomethyleneindanone-based compounds were synthesized:compound V and compound IX. The following non-disrupteddicyanomethyleneindanone-based compounds were also synthesized: compoundXXIX and compound XXX. The following core disrupted indandione-basedcompounds were also synthesized: compound XIII and compound XVII. Thefollowing non-disrupted indandione-based compounds were alsosynthesized: compound XXXII.

The synthesized photoactive compounds were subjected to purification byvacuum sublimation and the results are summarized in FIG. 37, whichshows a plot of the maximum sublimation yield of each compound as afunction of molecular weight. Compound XI had a maximum sublimationyield of 13.5%, compound IX had a maximum sublimation yield of 46.3%,compound XXIX had a maximum sublimation yield of 0%, compound XXX had amaximum sublimation yield of 0%, compound XIII had a maximum sublimationyield of 85.7%, compound XVII had a maximum sublimation yield of 91.3%,and compound XXXII had a maximum sublimation yield of 31.1%,

Sublimation yields of the non-disrupted photoactive compounds (emptypoints on FIG. 37) and the core disrupted photoactive compounds (filledpoints on FIG. 37) were compared to see the effects of core disruptionat the electron donor moiety. The change from non-disrupted photoactivecompounds XXIX, XXX, and XXXII to counterpart core disrupted photoactivecompounds XI, IX, and XIII respectively showed increases in sublimationyield of 13.5%, 46.3%, and 54.6%. These results indicate that use ofcore-disruption in electron donor moieties may be a suitable techniquefor achieving high volatility and enable compatibility with physicalvapor deposition.

Sublimation yields of the dicyanomethyleneindanone-based photoactivecompounds (circular points on FIG. 37) and the indandione-basedphotoactive compounds (diamond points on FIG. 37) were compared to seethe effects of the change of electron acceptor moiety fromdicyanomethyleneindanone to indandione. The change fromdicyanomethyleneindanone-based compounds XI, IX, and XXIX to counterpartindandione-based compounds XIII, XVII, and XXXII respectively showedincreases in sublimation yield of 72.2%, 45%, and 31.1%. These resultsindicate that use of indandione in electron acceptor moieties may be asuitable technique for achieving high volatility and enablecompatibility with physical vapor deposition.

EXAMPLE 5—TRANSPARENT PHOTOVOLTAIC DEVICES COMPRISING PHOTOACTIVECOMPOUNDS CONTAINING CORE DISRUPTION AND INDANDIONES

FIG. 38 illustrates absorption coefficients for exemplary active layermaterials that can be utilized in various examples described herein. Theabsorption coefficients were determined from films of compounds IX,XIII, XVII, and LXXV deposited through vacuum thermal evaporation. Asillustrated in FIG. 38, the active layer materials can be characterizedby strong absorption peaks in the red to NIR regions of the solarspectrum. Strong optical transitions at these long wavelengths confirmthe preservation of molecular structure through the vacuum thermalevaporation process, in which similar molecules without core-disruptionor indandione units may decompose. Although spectra of particularexemplary compounds are illustrated in FIG. 38, examples are not limitedto the particular example compound and other photoactive compounds canbe utilized in various examples and embodiments.

FIGS. 39A-D illustrate transparent photovoltaic device structures3900-3903, according to several examples. Device structures 3900-3903comprise either a bulk heterojunction (BHJ) or planar-mixedheterojunction (PMHJ) active layer between a top electrode and a bottomelectrode that contains a core-disrupted compound or molecule as anactive material, which may be formed on a substrate through vacuumthermal evaporation, as described herein. In some examples, thecore-disrupted molecule also contains indandione acceptor groups. TheITO layer may correspond to the anode. The MoO₃ layer may function as ahole injection layer and may be considered part of the anode structureor as a buffer layer coupled to the anode. The para-sexiphenyl (p-6P)layer may be considered as a buffer layer coupled to the anode. The Aglayer may correspond to the cathode. The TPBi:C₆₀ layer may beconsidered part of the cathode structure or as a buffer layer coupled tothe cathode. The TPBi layer may correspond to an optical layer or as anencapsulating layer to the cathode. Although a particular exemplaryelectron donor (or acceptor) is illustrated in FIG. 39, such aconfiguration is not limiting and other donors and/or acceptors can beutilized according to various examples.

FIG. 39A illustrates a transparent photovoltaic device structure 3900,according to one example. Device structure 3900 comprises a binary BHJactive layer between a top electrode and a bottom electrode thatcontains ClAlPc as an electron donor and a core-disrupted molecule,compound IX, as an electron acceptor, formed through vacuum thermalevaporation. In some examples, the ClAlPc:IX blend is maintained at adonor to acceptor ratio of 50:50.

FIG. 39B illustrates a transparent photovoltaic device structure 3901,according to one example. Device structure 3901 comprises a ternary BHJactive layer between a top electrode and a bottom electrode thatcontains TAPC and the core-disrupted and indandione-containing compoundXIII as electron donors and fullerene C₆₀ as an electron acceptor,formed through vacuum thermal evaporation. In some examples, theTAPC:XIII:C₆₀ blend is maintained at a donor:donor:acceptor ratio of10:10:80.

FIG. 39C illustrates a transparent photovoltaic device structure 3902,according to one example. Device structure 3902 comprises a PMHJ activelayer between a top electrode and a bottom electrode that contains SubNcas an electron donor and the core-disrupted and indandione-containingcompound XVII as an electron acceptor, formed through vacuum thermalevaporation. In some examples, the SubNc:XVII blend is maintained at adonor to acceptor ratio of 50:50, and thin layers of SubNc and XVII arecoupled to the blend layer.

FIG. 39D illustrates a transparent photovoltaic device structure 3903,according to one example. Device structure 3903 comprises a binary BHJactive layer between a top electrode and a bottom electrode thatcontains the indandione-containing compound LXXV as an electron donorand fullerene C₇₀ as an electron acceptor, formed through vacuum thermalevaporation. In some examples, the LXXV:C₇₀ blend is maintained at adonor to acceptor ratio of 30:70.

FIGS. 40A-C illustrate current density-voltage curves (FIG. 40A),external quantum efficiency (EQE) curves (FIG. 40B), and transmissionspectra (FIG. 40C) for the device structures shown in FIGS. 39A-39D.Specifically, the solid lines correspond to device structure 3900, thedashed lines correspond to device structure 3901, the dash-dotted linescorrespond to device structure 3902, and the dotted lines correspond todevice structure 3903. As can be seen in FIG. 40A, all devices showstrong rectification in forward-bias and photocurrent and powerproduction under 1-sun illumination (AM1.5G spectrum) conditions. Thephotocurrents are confirmed to have significant contributions from theactive compounds IX, XIII, XVII, and LXXV based on the EQE spectra inFIG. 40B and their corresponding absorption coefficients in FIG. 38. Thetransparency of the photovoltaic devices is confirmed by theirtransmission spectra in FIG. 40C.

Table 1 tabulates the electrical and optical device performance datafrom the current density-voltage curves (FIG. 40A) and transmissionspectra (FIG. 40C) for the device structures shown in FIGS. 39A-39D.Specifically, the data for compound IX corresponds to device structure3900, the data for compound XIII corresponds to device structure 3901,the data for compound XVII corresponds to device structure 3902, and thedata for compound LXXV corresponds to device structure 3903. Thecore-disrupted or indandione-containing molecules are listed in terms oftheir function in the active layer (electron donor or electronacceptor), the other active materials paired with them, and the deviceparameters short-circuit current density (J_(sc)), open-circuit voltage(V_(oc)), fill factor (FF), power conversion efficiency (PCE), andaverage visible transmittance (T_(vis)). As can be seen, all devices3900-3903 exhibit T_(vis) values above 50%, highlighting thecompatibility of the example molecules for transparent photovoltaics.

TABLE 1 Device Performance Summary J_(sc) V_(OC) PCE T_(vis) CompoundFunction Pairing (mA cm⁻²) (V) FF (%) (%) IX Acceptor ClAlPc 1.79 0.500.36 0.32 65.9 XIII Donor TAPC, 3.33 0.87 0.54 1.57 68.4 C₆₀ XVIIAcceptor SubNc 2.68 0.76 0.48 0.99 57.3 LXXV Donor C₇₀ 4.74 0.85 0.632.57 67.9

STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS

All references throughout this disclosure, for example patent documentsincluding issued or granted patents or equivalents; patent applicationpublications; and non-patent literature documents or other sourcematerial; are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference.

All patents and publications mentioned in this disclosure are indicativeof the levels of skill of those skilled in the art to which theinvention pertains. References cited herein are incorporated byreference herein in their entirety to indicate the state of the art, insome cases as of their filing date, and it is intended that thisinformation can be employed herein, if needed, to exclude (for example,to disclaim) specific embodiments that are in the prior art. Forexample, when a compound is claimed, it should be understood thatcompounds known in the prior art, including certain compounds disclosedin the references disclosed herein (particularly in referenced patentdocuments), are not intended to be included in the claim.

When a group of substituents is disclosed herein, it is understood thatall individual members of those groups and all subgroups and classesthat can be formed using the substituents are disclosed separately. Whena Markush group or other grouping is used herein, all individual membersof the group and all combinations and subcombinations possible of thegroup are intended to be individually included in the disclosure. Asused herein, “and/or” means that one, all, or any combination of itemsin a list separated by “and/or” are included in the list; for example“1, 2 and/or 3” is equivalent to “‘1’ or ‘2’ or ‘3’ or ‘1 and 2’ or ‘1and 3’ or ‘2 and 3’ or ‘1, 2 and 3’”.

Every formulation or combination of components described or exemplifiedcan be used to practice the invention, unless otherwise stated. Specificnames of materials are intended to be exemplary, as it is known that oneof skill in the art can name the same material differently. It will beappreciated that methods, device elements, starting materials, andsynthetic methods other than those specifically exemplified can beemployed in the practice of the invention without resort to undueexperimentation. All art-known functional equivalents, of any suchmethods, device elements, starting materials, and synthetic methods areintended to be included in this disclosure. Whenever a range is given inthe specification, for example, a temperature range, a time range, or acomposition range, all intermediate ranges and subranges, as well as allindividual values included in the ranges given are intended to beincluded in the disclosure.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of” excludes any element, step, or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof” does not exclude materials or steps that do not materially affectthe basic and novel characteristics of the claim. Any recitation hereinof the term “comprising”, particularly in a description of components ofa composition or in a description of elements of a device, is understoodto encompass those compositions and methods consisting essentially ofand consisting of the recited components or elements. The inventionillustratively described herein suitably may be practiced in the absenceof any element or elements, limitation or limitations which is notspecifically disclosed herein.

Abbreviations that may be utilized in the present specification include:

p-6P: 1-phenyl-4-[4-[4-(4-phenylphenyl)phenyl]phenyl]benzeneTPBi: 2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)

ClAlPc: Chloro(29H,31H-phthalocyaninato)aluminum SubNc:Chloro(subphthalocyaninato)boron

TAPC: 4,4′-Cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine]

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by preferred examplesand embodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered withinthe scope of this disclosure as defined by the appended claims.

What is claimed is:
 1. A photoactive compound having the formula: A-D-A,A-pi-D-A, A-pi-D-pi-A, A-D, or A-pi-D, wherein A is an electron acceptormoiety, wherein pi is a π-bridging moiety, wherein D is an electrondonor moiety, and wherein at least one A comprises an imine bond linkingthe electron acceptor moiety to the electron donor moiety or theπ-bridging moiety.
 2. The photoactive compound of claim 1, having amolecular weight of from 250 atomic mass units to 1200 atomic massunits.
 3. The photoactive compound of claim 1, characterized by orexhibiting a sublimation purification yield by mass of 20% or greater.4. The photoactive compound of claim 1, having a thermal decompositiontemperature of from 200° C. to 500° C.
 5. The photoactive compound ofclaim 1, exhibiting a bandgap of 0.5 eV to 4.0 eV.
 6. The photoactivecompound of claim 1, exhibiting a sublimation temperature of from 150°C. to 450° C. at pressures of from 0.2 Torr to 10⁻⁷ Torr.
 7. Thephotoactive compound of claim 1, wherein at least one A comprises

wherein A′ is an imine-linked electron acceptor moiety.
 8. Thephotoactive compound of claim 7, wherein each A comprises

wherein A′ is an imine-linked electron acceptor moiety.
 9. Thephotoactive compound of claim 7, wherein A′ comprises a heterocycle. 10.The photoactive compound of claim 7, wherein at least one A comprises animine-linked indandione, an imine-linked dicyanomethyleneindanone, animine-linked bis(dicyanomethylidene)indan, or an imine-linkeddicyanovinylene.
 11. The photoactive compound of claim 1, wherein atleast one A comprises:

wherein each R is independently H, F, Cl, Br, I, CH₃, CF₃, or CN,wherein each Y¹ is independently C(CN)₂, O, S, or cyanoimine, andwherein Y² is CH or N or Y² is not present and the A is connected to a Dmoiety or a pi moiety by a double bond, wherein each X¹ is independentlyO, S, Se, or NR^(O), wherein each R³ is CN or C(CN)₂, and wherein R^(O)is a branched or straight chain alkyl group having a molecular weight offrom 15 amu to 100 amu.
 12. The photoactive compound of claim 1,comprising A″-D-A, A″-pi-D-A, A-pi-D-A″, A″-pi-D-pi-A, or A″-pi-D-pi-A,wherein A″ is a carbon linked electron acceptor moiety.
 13. Thephotoactive compound of claim 1, wherein each pi independentlycomprises:

wherein each X¹ is independently O, S, Se, or NR^(N), wherein each R isindependently H, F, Cl, Br, I, CH₃, CF₃, or CN, wherein each X² isindependently O, S, Se, NH, NR^(N), CH₂, or C(R^(N))₂, wherein each W isindependently H, F, or a branched or straight chain C1-C8 alkyl group ora branched or straight chain C1-C8 alkoxy group, and wherein each R^(N)is independently a branched, cyclic, or straight chain alkyl or estergroup having a molecular weight of from 15 amu to 100 amu.
 14. Thephotoactive compound of claim 1, wherein D comprises an aromatic,heteroaromatic, polycyclic aromatic, or polycyclic heteroaromatic moietyincluding one or more 5-membered rings, one or more 6-membered rings, ora combination of one or more 5-membered rings and one or more 6-memberedrings.
 15. The photoactive compound of claim 1, wherein D comprises orhas a formula of

wherein each X is independently O, S, Se, NH, NR^(N), CH₂, C(R^(N))₂,Si(R^(N))₂, or Ge(R^(N))₂, wherein R^(N) is a branched, cyclic, orstraight chain alkyl or ester group having a molecular weight of from 15amu to 100 amu, wherein each W is independently H, F, or a branched orstraight chain C1-C8 alkyl group or a branched or straight chain C1-C8alkoxy group, wherein each R is independently H, F, Cl, Br, I, CH₃, CF₃,or CN, wherein Y³ is independently O or S, wherein Q is a quaternarycenter, wherein Y⁴ is independently CH, N, or CR^(N), and wherein each Zis independently a substituted or unsubstituted alkyl group, asubstituted or unsubstituted alkenyl group, an unsubstituted or methyl,ethyl, fluoro, or trifluoromethyl substituted cycloalkyl group, anunsubstituted or methyl, ethyl, fluoro, or trifluoromethyl substitutedcycloalkenyl group, an unsubstituted or methyl, ethyl, fluoro, ortrifluoromethyl substituted cyclopentadienyl group, or an unsubstitutedor methyl, ethyl, fluoro, or trifluoromethyl substituted phenyl group;or two Zs together form an unsubstituted or methyl, ethyl, fluoro, ortrifluoromethyl substituted cycloalkyl group, an unsubstituted ormethyl, ethyl, fluoro, or trifluoromethyl substituted cycloalkenylgroup, an unsubstituted or methyl, ethyl, fluoro, or trifluoromethylsubstituted cyclopentadienyl group, or an unsubstituted or methyl,ethyl, fluoro, or trifluoromethyl substituted phenyl group; or two Zstogether form a group containing fused 5-membered rings that areunsubstituted or methyl, ethyl, fluoro, or trifluoromethyl substituted,fused 6-membered rings that are unsubstituted or methyl, ethyl, fluoro,or trifluoromethyl substituted, or fused 5-membered and 6-membered ringsthat are unsubstituted or methyl, ethyl, fluoro, or trifluoromethylsubstituted; or two Zs together form a heterocyclic group or a fusedheterocyclic group.
 16. The photoactive compound of claim 1, wherein Dcomprises a central core and one or more planarity disrupting moieties,Z, attached to the central core, wherein the central core has a planarstructure, and wherein the one or more planarity disrupting moieties, Z,are conformationally locked in a configuration out of plane to thecentral core.
 17. The photoactive compound of claim 1, having a formulaof


18. A photovoltaic device comprising: a substrate; a first electrodecoupled to the substrate; a second electrode above the first electrode;a first photoactive layer between the first electrode and the secondelectrode, wherein the first photoactive layer comprises the photoactivecompound of claim 1; and a second photoactive layer between the firstelectrode and the second electrode, wherein the second photoactive layercomprises a counterpart electron donor material or a counterpartelectron acceptor material, and wherein the first photoactive layer andthe second photoactive layer correspond to separate photoactive layers,partially mixed photoactive layers, or a fully mixed photoactive layer.19. The photovoltaic device of claim 18, wherein one or more or all ofthe substrate, the first electrode, the second electrode, the firstphotoactive layer, or the second photoactive layer is visiblytransparent.
 20. The photovoltaic device of claim 18, wherein one ormore of the substrate, the first electrode, the second electrode, thefirst photoactive layer, or the second photoactive layer is partiallytransparent or opaque.
 21. The photovoltaic device of claim 18, whereinthe photoactive compound of claim 1 is an electron acceptor compound andwherein the second photoactive layer comprises a counterpart electrondonor material.
 22. The photovoltaic device of claim 18, wherein thephotoactive compound of claim 1 is an electron donor compound andwherein the second photoactive layer comprises a counterpart electronacceptor material.
 23. A method of making a photovoltaic device, themethod comprising: providing a substrate; providing a first electrodecoupled to the substrate; depositing a photoactive layer over thevisibly transparent electrode and visibly transparent substrate by avapor deposition technique, the photoactive layer comprising thephotoactive compound of claim 1; and providing a second electrode overthe photoactive layer.
 24. The method of claim 23, wherein depositingthe photoactive layer comprises depositing the photoactive compoundusing a thermal evaporation process.
 25. The method of claim 23, whereinone or more or all of the substrate, the first electrode, the secondelectrode, or the photoactive layer is visibly transparent.
 26. Themethod of claim 23, wherein one or more of the substrate, the firstelectrode, the second electrode, or the photoactive layer is partiallytransparent or opaque.